CA1111637A - Developing apparatus - Google Patents
Developing apparatusInfo
- Publication number
- CA1111637A CA1111637A CA303,673A CA303673A CA1111637A CA 1111637 A CA1111637 A CA 1111637A CA 303673 A CA303673 A CA 303673A CA 1111637 A CA1111637 A CA 1111637A
- Authority
- CA
- Canada
- Prior art keywords
- developer
- toner
- developing apparatus
- sensor
- sump
- 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.)
- Expired
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
- G03G15/0822—Arrangements for preparing, mixing, supplying or dispensing developer
- G03G15/0848—Arrangements for testing or measuring developer properties or quality, e.g. charge, size, flowability
- G03G15/0849—Detection or control means for the developer concentration
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Dry Development In Electrophotography (AREA)
- Control Or Security For Electrophotography (AREA)
Abstract
IMPROVED DEVELOPING APPARATUS
ABSTRACT OF THE DISCLOSURE
If developer within a xerographic developing app-aratus becomes excessively charged, excessive toner is added to the apparatus because the excessively charged developer prevents a sensor from sensing the actual toner density within the apparatus. To overcome this problem, an element (contacted by the developer during movement of the latter within the apparatus) is connected to ground through a surge voltage protector. This prevents both the element and the developer from being excessively charged.
ABSTRACT OF THE DISCLOSURE
If developer within a xerographic developing app-aratus becomes excessively charged, excessive toner is added to the apparatus because the excessively charged developer prevents a sensor from sensing the actual toner density within the apparatus. To overcome this problem, an element (contacted by the developer during movement of the latter within the apparatus) is connected to ground through a surge voltage protector. This prevents both the element and the developer from being excessively charged.
Description
~ D~ ~
ACKGROUND OF r~HE INVENTION
The present invention relates to an improved developing apparatus for an electrostatic reproduction machine.
In conventional xerography, a xerographic pla-te (photoreceptor) comprising a layer of photosensitive in-sulating material affixed to a conductive backing is used to support electrostatic latent images. In the xerographic process, the photosensitive surface is electrostatically charged, and the charged surface is then exposed to a light pattern of the image being reproduced to thereby discharge the surface in the areas where light strikes the surface.
The undischarged areas of the surface thus form an electro-static charge pattern (an electrostatic latent image) conforming to the original pattern. The latent image is then 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. Where the charge is greater, a greater amount of toner is deposited. Thus, a toner image is produced in conformity with a light image of the copy being reproduced. Generally, the developed image is then transferred to a suitable transfer member (e.g., paper) and the image is affixed thereto to form a permanent record of the original document.
In the practice of xerography, the transfer member is caused to move in synchronized contack with the photo-receptor surface during the transfer operation, and an electrical potential opposite from the polarity of the toner is applied to the side of the paper remo-te from the photoreceptor to electrostatically attract the toner image from the photoreceptor to the paper.
A modern high speed duplicating machine uses a developing apparatus having magnetic brushes to transport developer (carrier plus toner) from a developer sump to the photoreceptor to develop the latent image. Toner is periodically dispensed into the developer sump by a toner dispensing device, the latter being actuated by a sensor and control means in accordance with the sensed density of toner alternately deposited on either of two attracting elements. The amount of useful toner particles in the developer can be determined by the amount that will be alternately deposited upon the elements, each being charged with a voltage to set up the proper field between the elements. This toner determination is utilized to control the amount of active toner within the apparatus. The sensor, having two elements each capable of carrying a charge placed thereon, is positioned within the apparatus to receive some of the developing material falling between the elements. Potentials are alternately placed upon the elements cyclically, thereby reversing the electric field between the elements cyclically. This causes toner to be attracted to and cleaned from the elements cyclically.
While one element is provided with an attracting field, the other element serves as a ~evelopment electrode ~or the solid area development of the attracting element since the electric field between the elements will be uniform. The amount of toner attracted to each element when lt is charged to attract toner for any particular period of kime is related to or a function of the developability in the developer ~3 apparatus. The elements are connected in an elec~rical circuit which produces a steady state signal set for optimum condition and which, when devia~ed from a preset level, generates a control signal introducing toner particles into the developer sump. Such a sensor and control means is thoroughly described in U.S. Patent No. 3,727,06~ assigned to Xerox Corporation.
Included in the above describe~ developing apparatus is a screen through which the developer passes before reach-ing the sensor, the screen separating contaminates from thedeveloper be~ore the latter reaches the sensor. One of the problems with this arrangement is that the screen ~ecomes clogged with developer after only a few thousand copies are made. When the screen becomes clogged, very little or no developer reaches the sensor J and this causes the sensor to actuate the toner dispenser an excessive amount. Consequently, an excessive amount of toner is dispensed into the developer sump, and this eventually causes the machine to go into a ~ailure mode in which copy quality deteriorates, the machine cleaning system fails, photoreceptor filming occurs, etc. This problem is magnified when a duplicating machine is operating in areas of low humidity.
~ he app~icants discovered that the reason the de~oper was accumulating on and clogging the screen was because the developer was becoming excessively charged.
Upon discovering this, attempts were made by others (without success) to discover the reason for the excessive charging. The applicants eventually discovered that the i3~
reason the developer was becoming exce~sively char~ed wasbecause an electrically isolated guide plate in the de~elop-ing apparatus was becoming excessively charged and eventually caused the developer to become excessively charged through direct contact. ~fter this became known, others suggested that either electrically biasing the guide plate or ground-ing the plate would solve the pxoblem. Neither suggestion proved successful.
After further investigation, the applicants then discovered that the spacing between the guide plate and one of the magnetic brushes was critical because if this spacing was within extremely close tolerances, the charge on the guide plate would discharge to the magnetic brush before the mag-nitude of the charge became sufficient to cause the developer to clog the screen. The applicants eventually discovered, however, that this spacing could not be controlled to the degree necessary because variants in the manufacturing pro-cess actually caused direct contact between the magnetic brush and the guide plate most of the time when the spacing was adjusted to the extremely close tolerances necessary.
Conse~uently, the applicants concluded that what was necessary was to control the magnitude of the charge build-up on the guide plate by other means so that the spacing between the plate and the magnetic brush only had to be nominally adjusted.
SUMMARY OF THE INVENTION
An object of an aspect of the present invention is to control the magnitude of the charge on developer contained t~37 within a developing apparatus. This is effected by con-necting a guide plate ~which the developer contac-ts) to ground through a surge voltage protector.
An aspect of the invention is as follows:
An improved developing apparatus for developing an electrostatic latent image on a photoreceptor, the developing apparatus including a developer housing defining a sump for containing developer comprising carrier beads and toner particles, a sensor for control-ling the dispensing of additional toner into the sump,means for transporting toner from the sump to the photo-receptor to develop the latent image, and means for - directing developer from the transporting means to the sensor before ~eing returned to the sump, the improve-~ment comprising: a surge voltage protector; and means for electrically grounding said directing means through said surge voltage protector to control the magnitude of the charge on the de~eloper directed to the sensor.
-5a-3~
BRIEF DESCRIPTION OF I~IE DRAWING
The Figure is a schematic sectional view of an electrostatic reproduction machine embodying the p~inciples of the present invention.
DETAILED DESC~IPTION OF ~IE INVENTION
For a general understanding of an electrostatic reproduction machine in which the present invention may be incorporated, reference is made to Figure 1. As in all electrostatic reproduction machines of the type illustrated, a light image of an original is projected onto the photo-sensitive surface of a xerographic plate to ~orm an electro-static latent image thereon. Thereafter, the latent image is developed with developer comprising carrier beads and toner particles triboelectrically adhering thereto to form a xerographic powder image corresponding to the latent image on the photosensitive surface. The powder image is then electrostatically transferred to a trans~er member such as a sheet of paper to which it may be fixed by a fu~ing device whereby the toner image is caused permanently to adhere to the transfer member.
In the illustrated machine 10, an original 12 to be copied is placed upon a transparent support platen 14 fixedly arranged in an illumination assembly indicated generally by the reference numeral 16. While upon the platen, the illumination assembly flashes light rays upon the original, thereby producing image rays corresponding to the informational areas on the orig;nal. The ~mage rays are projected by means of an optical system 18 to an exposure station 20 for exposiny the surface of a moving xerographic plate in the form o~ a ~lexible photoconductive belt or photoreceptor 22. In moving in the direction indicated by the arrow, prior to reaching ~he exposure station 20, that portion of the belt being e~posed would have been uniformly charged to approximately ~900 volts by a corona generating device 24 located at a belt run e~-tending between ~elt supporting rollers 26 and 28. The e~posure station extends between the roller 28 and a third roller 30.
The exposure of the photosensitive surface of the belt to the light image discharges ~he surface in the areas struck by light whereby an electrostatic latent image remains on the belt in image con~iguration corresponding to the light image projected from the original on the support platen.
As the belt continues its movement, the latent image passes around the roller 30 and through a developing station 32 where a developing apparatus indicated generally b~ the reference numeral 34 is positioned. The developing apparatus 34 comprises a plurality of magnetic brushes 36 which carry developer to the surface of the upwardly moving belt 22.
Magnetic brushes are well known in the art, each such brush including stationary magnets located within a non-magnetic conductive sleeve or cylinder, the latter being electrically biased to a value slightly above the background potential on the photoreceptor. As developer is applied to the belt, toner particles in the development material are electro-statically attracted to the charged photosensitive sur~ace to form a powder image (a developed electrostatic image).
The developed electrostatic imaye is transported by the belt 22 to a transfer station 3~ where a sheet of paper is moved at a speed in synchro~ism with the moving belt in order to e~fect transfer o~ the developed imaye.
Located at the transfer station 38 is a trans~er roll 40 which is arranged on the frame of the machine to contact the back siae of the sheet oi paper as the latter is moved or fed between the belt and the transfer roll. The roll 30 is electrically biased with sufficient voltaye so that the developed image on the belt may be electrostatically attracted to the adjacent side of a sheet of paper as the latter is brought into contact therewith. The transfer is ini~iated by the transfer roll 40, but is completed by a corona generating device 42.
A suitable sheet transport mechanism transports sheets of paper seriatim from a paper handling mechanism indicated generally by the reference numeral 44 ko the developed image on the belt as the same is carried around the roller 26. In passing from the paper handling mechanism to the trans~er roll 40, each sheet contac~s a plurality of registration fingers 46.
As a sheet emerges from the transfer station 38, a charge is deposited thereon by a detack corona generating device 48 to lessen the electrostatic attraction ~etween the belt 22 and the sheet so that the latter can be removed by a vacuum stripping and transport mechanism 50. The sheet is thereafter retained on the underside of the vacuum stripping transport mechanism 50 for movement into a fuser assembly indicated generally by the reference numeral 52 wherein the powder image on the sheet is permanently affixed thereto.
After fusing, the finished copy is discharged at a suitable point for collection. The toner particles remaininy as residue on the belt 22 are carried by the belt to a cleaning ~ 3 ~
apparatus 54. The cleaning apparatus 54 comprises a corona discharge device 56 for neutraliziny charges remaining on the un-transferred toner particles, a rotating brush 58 mounted within a housing 60, and a vacuum outlet 62.
The developing apparatus 34 includes a sump 64 for containing developer, and developer is transported ~rom the sump to the photoreceptor by the magnetic brushes 36.
Depleted developer is returned by gravity to the sump from the uppermost magnetic brush, the developer being directed by guide plate 66 to a screen 68. A portion of the developer impacting the screen 68 passes throuyh the screen and through a sensor 70. The sensor and control means are thoroughly described in U.S. Patent ~o. 3,727,065 assigned to Xerox Corporation. As described above, however, the sensor 70 includes two elements for sensing toner density, the sensor and control means actuating a toner dispenser 72 when the density falls below a predetermined value. upon actuation of the toner dispenser, a foam roll 74 rotates to dispense toner into the sump 64.
To overcome the problem described above, i.e. 7 clogglng of the screen 68 by excessively charged developer, the guide plate 66 is connected to ground through a surge voltage protector 76. A suitable device for this purpose is a Siemens gas filled surge voltage protector, part number B2--B800. This device consists o~ electrodes spaced by glass or ceramic insulators. The electrodes are bonded to the insulator and form a hermeti.cally ~ealed discharge chamber which contains an inert gas. ~his permits the guide plate 66t and consequently the developer contactiny the plate, X _ g _ to be charged only to a predetermined magnitude By con-trolling the magnitude of the charge on the developer in this manner, the screen does no-t become clogged by developer, and consequently the toner dispenser 72 is actuated only when additional toner is actually required in the developing apparatus.
It is within the scope of the present invention to apply this principle to any other element of the developing apparatus which may be causing developer to become excessively charged. For example, the toner baffle plate 78 may also be connected to ground through a second surge voltage protector 80. While the invention has been described with reference to the structure disclosed, it is not confined to the details set forth, but is intended to cover such modifications or changes as may come within the scope of the following claims.
ACKGROUND OF r~HE INVENTION
The present invention relates to an improved developing apparatus for an electrostatic reproduction machine.
In conventional xerography, a xerographic pla-te (photoreceptor) comprising a layer of photosensitive in-sulating material affixed to a conductive backing is used to support electrostatic latent images. In the xerographic process, the photosensitive surface is electrostatically charged, and the charged surface is then exposed to a light pattern of the image being reproduced to thereby discharge the surface in the areas where light strikes the surface.
The undischarged areas of the surface thus form an electro-static charge pattern (an electrostatic latent image) conforming to the original pattern. The latent image is then 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. Where the charge is greater, a greater amount of toner is deposited. Thus, a toner image is produced in conformity with a light image of the copy being reproduced. Generally, the developed image is then transferred to a suitable transfer member (e.g., paper) and the image is affixed thereto to form a permanent record of the original document.
In the practice of xerography, the transfer member is caused to move in synchronized contack with the photo-receptor surface during the transfer operation, and an electrical potential opposite from the polarity of the toner is applied to the side of the paper remo-te from the photoreceptor to electrostatically attract the toner image from the photoreceptor to the paper.
A modern high speed duplicating machine uses a developing apparatus having magnetic brushes to transport developer (carrier plus toner) from a developer sump to the photoreceptor to develop the latent image. Toner is periodically dispensed into the developer sump by a toner dispensing device, the latter being actuated by a sensor and control means in accordance with the sensed density of toner alternately deposited on either of two attracting elements. The amount of useful toner particles in the developer can be determined by the amount that will be alternately deposited upon the elements, each being charged with a voltage to set up the proper field between the elements. This toner determination is utilized to control the amount of active toner within the apparatus. The sensor, having two elements each capable of carrying a charge placed thereon, is positioned within the apparatus to receive some of the developing material falling between the elements. Potentials are alternately placed upon the elements cyclically, thereby reversing the electric field between the elements cyclically. This causes toner to be attracted to and cleaned from the elements cyclically.
While one element is provided with an attracting field, the other element serves as a ~evelopment electrode ~or the solid area development of the attracting element since the electric field between the elements will be uniform. The amount of toner attracted to each element when lt is charged to attract toner for any particular period of kime is related to or a function of the developability in the developer ~3 apparatus. The elements are connected in an elec~rical circuit which produces a steady state signal set for optimum condition and which, when devia~ed from a preset level, generates a control signal introducing toner particles into the developer sump. Such a sensor and control means is thoroughly described in U.S. Patent No. 3,727,06~ assigned to Xerox Corporation.
Included in the above describe~ developing apparatus is a screen through which the developer passes before reach-ing the sensor, the screen separating contaminates from thedeveloper be~ore the latter reaches the sensor. One of the problems with this arrangement is that the screen ~ecomes clogged with developer after only a few thousand copies are made. When the screen becomes clogged, very little or no developer reaches the sensor J and this causes the sensor to actuate the toner dispenser an excessive amount. Consequently, an excessive amount of toner is dispensed into the developer sump, and this eventually causes the machine to go into a ~ailure mode in which copy quality deteriorates, the machine cleaning system fails, photoreceptor filming occurs, etc. This problem is magnified when a duplicating machine is operating in areas of low humidity.
~ he app~icants discovered that the reason the de~oper was accumulating on and clogging the screen was because the developer was becoming excessively charged.
Upon discovering this, attempts were made by others (without success) to discover the reason for the excessive charging. The applicants eventually discovered that the i3~
reason the developer was becoming exce~sively char~ed wasbecause an electrically isolated guide plate in the de~elop-ing apparatus was becoming excessively charged and eventually caused the developer to become excessively charged through direct contact. ~fter this became known, others suggested that either electrically biasing the guide plate or ground-ing the plate would solve the pxoblem. Neither suggestion proved successful.
After further investigation, the applicants then discovered that the spacing between the guide plate and one of the magnetic brushes was critical because if this spacing was within extremely close tolerances, the charge on the guide plate would discharge to the magnetic brush before the mag-nitude of the charge became sufficient to cause the developer to clog the screen. The applicants eventually discovered, however, that this spacing could not be controlled to the degree necessary because variants in the manufacturing pro-cess actually caused direct contact between the magnetic brush and the guide plate most of the time when the spacing was adjusted to the extremely close tolerances necessary.
Conse~uently, the applicants concluded that what was necessary was to control the magnitude of the charge build-up on the guide plate by other means so that the spacing between the plate and the magnetic brush only had to be nominally adjusted.
SUMMARY OF THE INVENTION
An object of an aspect of the present invention is to control the magnitude of the charge on developer contained t~37 within a developing apparatus. This is effected by con-necting a guide plate ~which the developer contac-ts) to ground through a surge voltage protector.
An aspect of the invention is as follows:
An improved developing apparatus for developing an electrostatic latent image on a photoreceptor, the developing apparatus including a developer housing defining a sump for containing developer comprising carrier beads and toner particles, a sensor for control-ling the dispensing of additional toner into the sump,means for transporting toner from the sump to the photo-receptor to develop the latent image, and means for - directing developer from the transporting means to the sensor before ~eing returned to the sump, the improve-~ment comprising: a surge voltage protector; and means for electrically grounding said directing means through said surge voltage protector to control the magnitude of the charge on the de~eloper directed to the sensor.
-5a-3~
BRIEF DESCRIPTION OF I~IE DRAWING
The Figure is a schematic sectional view of an electrostatic reproduction machine embodying the p~inciples of the present invention.
DETAILED DESC~IPTION OF ~IE INVENTION
For a general understanding of an electrostatic reproduction machine in which the present invention may be incorporated, reference is made to Figure 1. As in all electrostatic reproduction machines of the type illustrated, a light image of an original is projected onto the photo-sensitive surface of a xerographic plate to ~orm an electro-static latent image thereon. Thereafter, the latent image is developed with developer comprising carrier beads and toner particles triboelectrically adhering thereto to form a xerographic powder image corresponding to the latent image on the photosensitive surface. The powder image is then electrostatically transferred to a trans~er member such as a sheet of paper to which it may be fixed by a fu~ing device whereby the toner image is caused permanently to adhere to the transfer member.
In the illustrated machine 10, an original 12 to be copied is placed upon a transparent support platen 14 fixedly arranged in an illumination assembly indicated generally by the reference numeral 16. While upon the platen, the illumination assembly flashes light rays upon the original, thereby producing image rays corresponding to the informational areas on the orig;nal. The ~mage rays are projected by means of an optical system 18 to an exposure station 20 for exposiny the surface of a moving xerographic plate in the form o~ a ~lexible photoconductive belt or photoreceptor 22. In moving in the direction indicated by the arrow, prior to reaching ~he exposure station 20, that portion of the belt being e~posed would have been uniformly charged to approximately ~900 volts by a corona generating device 24 located at a belt run e~-tending between ~elt supporting rollers 26 and 28. The e~posure station extends between the roller 28 and a third roller 30.
The exposure of the photosensitive surface of the belt to the light image discharges ~he surface in the areas struck by light whereby an electrostatic latent image remains on the belt in image con~iguration corresponding to the light image projected from the original on the support platen.
As the belt continues its movement, the latent image passes around the roller 30 and through a developing station 32 where a developing apparatus indicated generally b~ the reference numeral 34 is positioned. The developing apparatus 34 comprises a plurality of magnetic brushes 36 which carry developer to the surface of the upwardly moving belt 22.
Magnetic brushes are well known in the art, each such brush including stationary magnets located within a non-magnetic conductive sleeve or cylinder, the latter being electrically biased to a value slightly above the background potential on the photoreceptor. As developer is applied to the belt, toner particles in the development material are electro-statically attracted to the charged photosensitive sur~ace to form a powder image (a developed electrostatic image).
The developed electrostatic imaye is transported by the belt 22 to a transfer station 3~ where a sheet of paper is moved at a speed in synchro~ism with the moving belt in order to e~fect transfer o~ the developed imaye.
Located at the transfer station 38 is a trans~er roll 40 which is arranged on the frame of the machine to contact the back siae of the sheet oi paper as the latter is moved or fed between the belt and the transfer roll. The roll 30 is electrically biased with sufficient voltaye so that the developed image on the belt may be electrostatically attracted to the adjacent side of a sheet of paper as the latter is brought into contact therewith. The transfer is ini~iated by the transfer roll 40, but is completed by a corona generating device 42.
A suitable sheet transport mechanism transports sheets of paper seriatim from a paper handling mechanism indicated generally by the reference numeral 44 ko the developed image on the belt as the same is carried around the roller 26. In passing from the paper handling mechanism to the trans~er roll 40, each sheet contac~s a plurality of registration fingers 46.
As a sheet emerges from the transfer station 38, a charge is deposited thereon by a detack corona generating device 48 to lessen the electrostatic attraction ~etween the belt 22 and the sheet so that the latter can be removed by a vacuum stripping and transport mechanism 50. The sheet is thereafter retained on the underside of the vacuum stripping transport mechanism 50 for movement into a fuser assembly indicated generally by the reference numeral 52 wherein the powder image on the sheet is permanently affixed thereto.
After fusing, the finished copy is discharged at a suitable point for collection. The toner particles remaininy as residue on the belt 22 are carried by the belt to a cleaning ~ 3 ~
apparatus 54. The cleaning apparatus 54 comprises a corona discharge device 56 for neutraliziny charges remaining on the un-transferred toner particles, a rotating brush 58 mounted within a housing 60, and a vacuum outlet 62.
The developing apparatus 34 includes a sump 64 for containing developer, and developer is transported ~rom the sump to the photoreceptor by the magnetic brushes 36.
Depleted developer is returned by gravity to the sump from the uppermost magnetic brush, the developer being directed by guide plate 66 to a screen 68. A portion of the developer impacting the screen 68 passes throuyh the screen and through a sensor 70. The sensor and control means are thoroughly described in U.S. Patent ~o. 3,727,065 assigned to Xerox Corporation. As described above, however, the sensor 70 includes two elements for sensing toner density, the sensor and control means actuating a toner dispenser 72 when the density falls below a predetermined value. upon actuation of the toner dispenser, a foam roll 74 rotates to dispense toner into the sump 64.
To overcome the problem described above, i.e. 7 clogglng of the screen 68 by excessively charged developer, the guide plate 66 is connected to ground through a surge voltage protector 76. A suitable device for this purpose is a Siemens gas filled surge voltage protector, part number B2--B800. This device consists o~ electrodes spaced by glass or ceramic insulators. The electrodes are bonded to the insulator and form a hermeti.cally ~ealed discharge chamber which contains an inert gas. ~his permits the guide plate 66t and consequently the developer contactiny the plate, X _ g _ to be charged only to a predetermined magnitude By con-trolling the magnitude of the charge on the developer in this manner, the screen does no-t become clogged by developer, and consequently the toner dispenser 72 is actuated only when additional toner is actually required in the developing apparatus.
It is within the scope of the present invention to apply this principle to any other element of the developing apparatus which may be causing developer to become excessively charged. For example, the toner baffle plate 78 may also be connected to ground through a second surge voltage protector 80. While the invention has been described with reference to the structure disclosed, it is not confined to the details set forth, but is intended to cover such modifications or changes as may come within the scope of the following claims.
Claims (4)
1. An improved developing apparatus for developing an electrostatic latent image on a photoreceptor, the developing apparatus including a developer housing defining a sump for containing developer comprising carrier beads and toner particles, a sensor for control-ling the dispensing of additional toner into the sump, means for transporting toner from the sump to the photo-receptor to develop the latent image, and means for directing developer from the transporting means to the sensor before being returned to the sump, the improve-ment comprising: a surge voltage protector; and means for electrically grounding said directing means through said surge voltage protector to control the magnitude of the charge on the developer directed to the sensor.
2. An improved developing apparatus as set forth in claim 1, wherein the directing means includes a screen for separating contaminates from the developer before the developer arrives at the sensor and a guide plate for directing the developer from the transport-ing means to the screen.
3. An improved developing apparatus as set forth in claim 2, wherein the surge voltage protector includes means defining a hermetically sealed discharge chamber for containing an inert gas, and a pair of electrodes within the chamber.
4. An improved developing apparatus as set forth in claim 3, wherein the developer transporting means includes at least one magnetic brush, and wherein the directing member is located adjacent to but spaced from the magnetic brush.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US80274977A | 1977-06-02 | 1977-06-02 | |
| US802,749 | 1977-06-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1111637A true CA1111637A (en) | 1981-11-03 |
Family
ID=25184583
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA303,673A Expired CA1111637A (en) | 1977-06-02 | 1978-05-18 | Developing apparatus |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS542136A (en) |
| CA (1) | CA1111637A (en) |
| DE (1) | DE2823805A1 (en) |
| GB (1) | GB1602774A (en) |
-
1978
- 1978-05-18 CA CA303,673A patent/CA1111637A/en not_active Expired
- 1978-05-25 JP JP6282478A patent/JPS542136A/en active Pending
- 1978-05-26 GB GB2322878A patent/GB1602774A/en not_active Expired
- 1978-05-31 DE DE19782823805 patent/DE2823805A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| GB1602774A (en) | 1981-11-18 |
| DE2823805A1 (en) | 1978-12-14 |
| JPS542136A (en) | 1979-01-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |