US3418972A - Powder dusting device for electrophotography - Google Patents

Powder dusting device for electrophotography Download PDF

Info

Publication number
US3418972A
US3418972A US684452A US68445267A US3418972A US 3418972 A US3418972 A US 3418972A US 684452 A US684452 A US 684452A US 68445267 A US68445267 A US 68445267A US 3418972 A US3418972 A US 3418972A
Authority
US
United States
Prior art keywords
powder
roller
duct
dusted
image carrier
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 - Lifetime
Application number
US684452A
Other languages
English (en)
Inventor
Obuchi Kazuo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fujifilm Holdings Corp
Original Assignee
Fuji Photo Film Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Fuji Photo Film Co Ltd filed Critical Fuji Photo Film Co Ltd
Application granted granted Critical
Publication of US3418972A publication Critical patent/US3418972A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
    • G03G15/34—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the powder image is formed directly on the recording material, e.g. by using a liquid toner
    • G03G15/342—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the powder image is formed directly on the recording material, e.g. by using a liquid toner by forming a uniform powder layer and then removing the non-image areas
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S222/00—Dispensing
    • Y10S222/01—Xerography

Definitions

  • a doctor plate positioned with a gap between the lower end of the doctor plate and the surface of the roller on the powder supply side of the roller in order to control the amount of powder being carried over on the roller surface
  • a duct arranged below the top of the rotating roller on the side opposite the powder supply side to receive powder which falls under the influence of gravity from the surface of the roller as said roller rotates
  • an air supply conduit provided at the upper end of the duct
  • corona discharge means provided at the lower end of said duct, whereby said powder is charged and uniformly dusted as a solid-gas sol onto an image carrier being moved at a constant speed and at a fixed distance below the outlet of said duct.
  • This invention relates to a device for dusting photoconductive powder over an image carrier in the electrophotography art.
  • the layer of powder should be uniform and the quantity of dusted powder should be even. Further, it has been experimentally verified that the tightness of powder layer affects the sharpness of the picture ob- .tained and, if the powder layer lacks tightness, the resulting picture lacks clarity, as compared to a tight powder layer, even if the same photoconductive powder is used and the same amount is dusted. Also, the tightness of the powder layer is related to the electric charge carried by each unit quantity of the dusted powder, and the tighter such a layer is, the greater is the electrostatic charge so held, and the better the picture obtained.
  • the layer of photoconductive powder which is tight and has a greater electrostatic charge is characterized by the fact that decay in the electrostatic potential of such a layer in the dark is considerably less than that of the same powder 3,418,972 Patented Dec. 31, 1968 that is not tight. This brings about a great advantage in such processes of photographic treatment, since the time from charging up to development is decreased.
  • the quantity of dusted powder per unit area affects the electrostatic charge or surface potential per unitarea of the image carrier. It is believed that the surface potential does not have as great an effect upon picture quality as the electrostatic charge held by the dusted powder per unit area and the uniformity of the electrostatic charge. With respect to surface potential, the quantity of dusted powder is not an important factor. However, if too much powder is dusted, the residual potential after exposure to light augments superlinearly, and the fog increases, causing the apparent photosensitivity of the powder layer to decrease. As a result, it becomes impossible to obtain a highly contrasted picture. Conversely, if too little powder is dusted, not only does the maximum density of the picture decrease, but the difference in the electrostatic force of attraction to the image carrier between the exposed and unexposed portions of the powder layer decreases sharply, thus making developing operations very difficult.
  • the quantity of electrostatic charge held by the powder layer should be adequate and uniform.
  • Devices utilized in this connection vary the quantity of electrostatic charge held per unit quantity of dusted powder according to the method of charging.
  • the following two methods have been considered: the first involves charging the powder after dusting it over the image carrier.
  • the powder may be dusted over the carrier using a vibrating sieve, a pneumatic sprinkler or the like, and then charged by utilizing a corona discharge method or the like. This method is generally known in electrophotography as the Carlson Method.
  • the second method of charging the powder involves charging the powder as it is dusted, or before it is dusted, over the image carrier.
  • the method which is known as the electrostatic powder coating method utilizes this sequence.
  • Devices for electrostatic powder coating which are commercially utilized include the r.e.p. gun made by the Japan Runsburg Company, and similar articles made by the Sames Company of France, the Hursant Company of Great Britain and others.
  • the r.e.p. gun of the Japan Runsburg Company is used for dusting photoconductive powder over the image carrier, good results may be obtained on a laboratory basis.
  • this electrostatic powder coating device to an actual electrophotographic apparatus using photoconductive powder would give rise to a number of problems.
  • the first problem is that where a copying apparatus utilizing photoconductive powder is required for business or industrial use, an electrostatic coating device such as mentioned above is not practical because it requires a large space in order to dust the powder.
  • large incidental devices such as a compressor and a super high-tension electric source are also required.
  • the present invention is intended to provide a powder dusting device for electrophotography which satisfies the above-mentioned requirements, and is applicable rnainly to electrophotographic apparatus such as electrophotoder dusting device for electrophotography, comprising:
  • a hopper a reservoir interconnected to an exit side of said hopper; a hopper gate for controlling the level of a photoconductive powder delivered from the exit of the hopper to the reservoir; a rotating roller having a powder supply side disposed within the reservoir so that said powder supply side is dipped in the powder, thereby carrying a layer of powder forward over its outer surface; a doctor plate positioned with a gap between the lower end of the doctor plate and the surface of the roller on the powder supply side of the roller to control the amount of powder being carried over on the roller upper surface; a duct arranged below the top of the rotating roller on the side opposite of the powder supply side to receive the powder which falls under gravity from the surface of the roller as said roller rotates; an air supply nozzle provided at the upper end of the duct; and corona discharge means provided at the lower end of said duct, whereby said powder is charged and uniformly dusted as a solid-gas sol onto an image carrier being moved at a constant speed and at fixed distance below the outlet of said duct.
  • the attached drawing shows a schematic diagram of a vertical side cross-section of a powder dusting device for use in electrophotography in accordance with this invention.
  • the numeral 1 denotes a hopper wall; 2 a hopper gate; 3 a roller capable of rotating in the direction of the arrow about its central axis; 4 a wall having a fixed space between it and the main wall 5 of the device to define an opening into which the photoconductive powder A falls; 6 a duct wide enough for the powder dusting breadth (perpendicular to the plane of the drawing) which consists of insulating walls provided below the above-mentioned opening; 7 a doctor plate which regulates the quantity of the powder carried to the roller rotating in the direction of the arrow; 8, 8 a pair of electrodes for corona discharge; 9 a DC.
  • B and C are the respective positions determined by the repose angle 6 of photo-conductive powder A and the roller 3, and represent the boundary lines between the upper surface of the layer of the powder A and the cylindrical surface of the roller 3.
  • the photoconductive powder A is put into the hopper 1 until it fills the powder reservoir formed by the bottom of the hopper 1, the wall 4 and the main wall 5 of the device.
  • the height of the surface of the powder layer delivered out of the hopper 1 is maintained constant by the hopper gate 2.
  • powder A is moved along the outer surface of the roller 3 by virtue of the friction between the powder and the outer surface of the roller 3, and is carried as a layer from the boundary line B to the right (in the drawing) over the upper surface of the roller.
  • the upper surface of the powder A in the powder reservoir, inclined at the repose angle 0 of the powder A is in contact with the upper surface of the roller 3.
  • a doctor plate 7 which is attached to the main wall 5 of the device. A space between the lower end of the plate and the outer surface of the roller is provided in order to regulate the quantity of powder carried by the roller 3, and thereby insure that a uniform quantity of powder is dusted.
  • the carried powder leaves the surface of the roller 3 on the opposite side to that of the powder supply, and thereafter passes through the opening formed between the wall 4 and the main wall 5 of the device and then through the duct 6, to be dusted down upon the upper surface of the image carrier which is proceeding forward in the direction indicated by the arrow in the drawing. Any powder sticking or adhering to the surface of the roller 3 is brought back into the aforementioned layer of powder through the space between the surface of the roller 3 and the upper end of the wall 4.
  • a current of air which is fed from a pneumatic source, such as a compressor or blower, through the air conduit 13 is adjusted in the pressure equalizing chamber 12 to a uniform pressure in the direction of the axis of rotation of the roller 3.
  • the air is mixed with the powder, and this mixture passes the lower end of the duct in the state of solid-gas sol.
  • the photoconductive powder is electrostatically charged by the corona discharge occurring on the lower end of the duct 6, and then is dusted uniformly over the image carrier 14 and is attached to the latter electrostatically.
  • a high voltage is provided to the corona discharge electrodes 8 from the high-voltage electrode of DC. hightension source 14 which has one end grounded.
  • the surface of the photo-conductive powder layer is kept inclined at a repose angle 6 as it touches the upper surface of the rotating roller 3, gOOd results can be obtained because it becomes possible to dust a smaller quantity of powder uniformly than when using a device which regulates the dusted quantity of powder by means of a doctor plate 7 alone without making use of the repose angle 0.
  • the powder is supplied to the upper surface of the roller 3 by merely utilizing the powder pressure, and the powder is dusted in quantities which are too large, and without uniformity.
  • an average particle diameter of 70 a particle diameter distribution of ESQ- the final rate of spontaneous falling due to the resistance of air will be about 0.3-0.5 m./ sec.
  • the powder stream may be uniform in the duct 6, it will produce considerable turbulence when it falls 5060 mm. after leaving the duct, and thus uniform dusting is made very diflicult.
  • the powder stream is disturbed by the corona wind originating from the electrodes, and this makes a uniform dusting impossible. For this reason, it becomes necessary to give the powder stream enough momentum for it to be able to withstand the influence of the corona wind or the air outside the duct. This is the reason why air is mixed with the powder stream in the middle portion of the duct in this invention.
  • the powder stream will not be adequately charged owing to the shortened period of time during which the powder is exposed to the ions produced from the corona discharge electrodes, and because of the lowered electrostatic force of attraction to the image carrier 14, part of the supplied powder will be blown away by the wind without attraction to the image carrier
  • the corona discharge electrodes those of various forms such as arrayed needles, saw teeth, knife edges, plates, small-diameter wires, etc. may be used. It is desirable that they produce uniform discharges in the direction of the axis of rotation of the roller 3.
  • the distance between the electrodes and the image carrier is comparatively large, it is difiicult to obtain uniform discharges by using electrodes other than those shaped like arrayed needles, or those shaped like large-pitch saw teeth.
  • the voltage to be applied to the corona discharge electrodes depends upon the electrode structure, the distance between the electrodes and the image carrier, but ordinarily the voltage is approximately 4 kv.-100 kv.
  • the polarity of the applied voltage is determined by the electrical characteristics of semiconductors contained in the photoconductive powder used, and when zinc oxide, cadmium sulphide and the like is used (as is usually the case) it is desirable that the polarity be negative.
  • the corona discharge electrodes are shown provided one on each side of the duct 6, making a total of two, but this does not necessarily mean that two of them are necessary. One alone on one side will suffice.
  • EXAMPLE 1 As the roller 3, a 60 mm. O.D. hard vinyl chloride pipe whose surface was painted with Dotite E3 electroconductive paint manufactured by Fujikura Kasei K.K. (an electroconductive paint with an electroconductive carbon black suspended in a water-based vinyl emulsion) was utilized.
  • the hopper gate 2 was so set that its pointed end might be positioned 35 mm. horizontally, and mm. vertically (upward) away from the center of the roller.
  • the duct 6, which was made of hard vinyl chloride was provided so as to measure 10 mm. across its inner space and 250 mm. in length. Close to the pointed end of the duct arrayed needle electrodes were provided having record needles (for SP) arrayed at an interval of 10 mm.
  • a photoconductive powder A which had a specific gravity of 1.54, an average diameter of 70 a particle diameter range of 30120p., and which comprised a transparent resin nucleus and a zinc oxide binder type photosensitive layer was dusted, with the following result: quantity dusted was 100 g./m. the irregularity of dusting was il0%, and a surface potential of 450 v. was realized. Upon exposure and development of the image carrier, there resulted a sharp and uniform picture.
  • the roller 3 was a 100 mm. O.D. brass cylinder whose surface was lathe-finished to a roughness of about 6-8.
  • the hopper gate 2 was provided so that its pointed end might be positioned 25 mm. horizontally, and 30 mm. vertically (upward) from the center of the roller 3.
  • the doctor plate 7 was installed with an interstice of 0.5 mm. between it and the roller so that its pointed end might be placed in the position determined by the angle of 55 which is formed between two planes intersecting with each other at the axis of rotation of the roller, one plane being horizontal and the other passing through the pointed end of the doctor plate 7.
  • the layout of the device in other respects was the same as that in case of Example I.
  • Example 1 With the roller 3 rotating at the rate of 35 r.p.m., the lower end of the duct 60 mm. distant from the image carrier, the image carrier being fed forward at the rate of 100 mm./sec., a wind velocity of 3 m./sec. at the lower end of the duct, and a voltage of kv. (minus) applied to the corona discharge electrodes, the same photoconductive powder A as was used in Example 1 was dusted, with the following result: quantity dusted was g./m. the irregularity of dusting was i5%, and a surface potential of 370 v. was realized. Upon exposure and development of the image carrier there resulted a sharp and uniform picture.
  • the irregularity of dusting represents the maximum value of deviation from the average value of the samples each having an area of 50 mm. square with respect to the average dusted quantity of powder.
  • a baflie plate (not illustrated) having a descending gradient toward the wall 4 is provided across the main wall 5 of the device and the wall 4 on each side in the direction of dusting breadth (perpendicular to the plane of the drawing) of the duct 6, the powder A does not fall into the duct 6 where the baffle plates stand, but is returned into the powder layer past the interstice between the wall 4 and the roller 3, and thereby it becomes possible to adjust the dusting breadth.
  • This fact is taken advantage of in case the breadth of the image carrier is different from piece to piece when the electrophotographic marking method is used.
  • a powder dusting device for electrophotography comprising: a hopper, a reservoir interconnected to an exit of said hopper, a hopper gate disposed at the interconnection between said hopper and said reservoir for controlling the level of a photoconductive powder delivered from the exit of the hopper to the reservoir, a rotating roller having a powder supply side disposed within the reservoir so that said supply side is dipped in the powder, thereby carrying a layer of powder forward over its outer surface, a doctor plate positioned with a gap between the lower end of the doctor plate and the surface of the roller on the powder supply side of the roller in order to control the amount of powder being carried over on the roller surface, a duct arranged below the top of the rotating roller on the side opposite the powder supply side to receive powder which falls under gravity from the surface of the roller as roller rotates, an air supply con-.
  • pressure equalizing means are provided between said air supply conduit and said duct.
  • said air supply conduit is selected so as to enable said solid-gas sol to attain an exit velocity of from about 1-10 m./ sec.
  • said corona discharge means are electrodes.
  • PETER FELDMAN Primary Examiner.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Photoreceptors In Electrophotography (AREA)
  • Electrostatic Spraying Apparatus (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
US684452A 1966-11-19 1967-11-20 Powder dusting device for electrophotography Expired - Lifetime US3418972A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP7604266 1966-11-19

Publications (1)

Publication Number Publication Date
US3418972A true US3418972A (en) 1968-12-31

Family

ID=13593729

Family Applications (1)

Application Number Title Priority Date Filing Date
US684452A Expired - Lifetime US3418972A (en) 1966-11-19 1967-11-20 Powder dusting device for electrophotography

Country Status (3)

Country Link
US (1) US3418972A (enrdf_load_stackoverflow)
GB (1) GB1169410A (enrdf_load_stackoverflow)
NL (1) NL6715543A (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3604981A (en) * 1969-12-19 1971-09-14 Nikka Kk Powder sprayer of high-tension discharge type
US4265196A (en) * 1976-09-27 1981-05-05 Am International, Inc. Toner applicator apparatus
US20040184840A1 (en) * 2003-03-21 2004-09-23 Xerox Corporation Ion toner charging device
US7013104B2 (en) 2004-03-12 2006-03-14 Lexmark International, Inc. Toner regulating system having toner regulating member with metallic coating on flexible substrate
US7236729B2 (en) 2004-07-27 2007-06-26 Lexmark International, Inc. Electrophotographic toner regulating member with induced strain outside elastic response region

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0197951A (ja) * 1987-10-09 1989-04-17 Brother Ind Ltd 画像形成媒体製造装置
US5060011A (en) * 1988-04-28 1991-10-22 Brother Kogyo Kabushiki Kaisha Image recording apparatus
US5038710A (en) * 1988-11-18 1991-08-13 Brother Kogyo Kabushiki Kaisha Developer material coating apparatus
JPH0290839U (enrdf_load_stackoverflow) * 1988-12-30 1990-07-18

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2027307A (en) * 1928-07-30 1936-01-07 Behr Manning Corp Method of coating and apparatus therefor and product
FR948978A (fr) * 1947-07-02 1949-08-17 Perfectionnements aux procédés de recouvrement d'objets, notamment pour la défense des cultures
US2742195A (en) * 1952-02-11 1956-04-17 Merck & Co Inc Dropper closure for containers
US2857879A (en) * 1955-09-01 1958-10-28 Abrasive Company Of America Apparatus for preparing abrasive articles
US2962381A (en) * 1957-07-02 1960-11-29 Congoleum Nairn Inc Segment wheel feeder
GB961989A (en) * 1961-04-13 1964-06-24 British Cellophane Ltd Improvements in or relating to apparatus for distributing powdered materials
US3238919A (en) * 1964-02-24 1966-03-08 Cra Vac Corp Apparatus for opposing offset in printing
US3363809A (en) * 1966-10-04 1968-01-16 George V. Wheeler Powder dispenser for printed webs

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2027307A (en) * 1928-07-30 1936-01-07 Behr Manning Corp Method of coating and apparatus therefor and product
FR948978A (fr) * 1947-07-02 1949-08-17 Perfectionnements aux procédés de recouvrement d'objets, notamment pour la défense des cultures
US2742195A (en) * 1952-02-11 1956-04-17 Merck & Co Inc Dropper closure for containers
US2857879A (en) * 1955-09-01 1958-10-28 Abrasive Company Of America Apparatus for preparing abrasive articles
US2962381A (en) * 1957-07-02 1960-11-29 Congoleum Nairn Inc Segment wheel feeder
GB961989A (en) * 1961-04-13 1964-06-24 British Cellophane Ltd Improvements in or relating to apparatus for distributing powdered materials
US3238919A (en) * 1964-02-24 1966-03-08 Cra Vac Corp Apparatus for opposing offset in printing
US3363809A (en) * 1966-10-04 1968-01-16 George V. Wheeler Powder dispenser for printed webs

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3604981A (en) * 1969-12-19 1971-09-14 Nikka Kk Powder sprayer of high-tension discharge type
US4265196A (en) * 1976-09-27 1981-05-05 Am International, Inc. Toner applicator apparatus
US20040184840A1 (en) * 2003-03-21 2004-09-23 Xerox Corporation Ion toner charging device
US7013104B2 (en) 2004-03-12 2006-03-14 Lexmark International, Inc. Toner regulating system having toner regulating member with metallic coating on flexible substrate
US7236729B2 (en) 2004-07-27 2007-06-26 Lexmark International, Inc. Electrophotographic toner regulating member with induced strain outside elastic response region

Also Published As

Publication number Publication date
GB1169410A (en) 1969-11-05
DE1597847B2 (de) 1975-10-02
NL6715543A (enrdf_load_stackoverflow) 1968-05-20
DE1597847A1 (de) 1970-08-20

Similar Documents

Publication Publication Date Title
US2725304A (en) Process for developing an electrostatic latent image
US3426730A (en) Apparatus for coating continuously moving strip material with powders
US2701764A (en) Electrophotographic apparatus and methods
US3418972A (en) Powder dusting device for electrophotography
US3430606A (en) Electroscopic particle sensor
US2868989A (en) Electrostatic charging method and device
JPS58182659A (ja) 電子写真装置における帯電方法
US4073266A (en) Apparatus for developing a latent electrostatic image on an electrophotographic copying material
US3005726A (en) Process of developing electrostatic images
US2856533A (en) Moving wire corona
US3566833A (en) Continuous coating apparatus
US2862646A (en) Powder particle aerosol generator
DE2308587C3 (de) Vorrichtung zur Messung der Tonerkonzentration eines pulverförmigen Entwicklers in einem elektrophotographischen Kopiergerät
US4431296A (en) Developing method and apparatus therefor
US2832511A (en) Generator of an aerosol of powder particles
US3331355A (en) Xerographic developing apparatus
US3898956A (en) Toner replenisher
US2878972A (en) Rough surface powder cloud generation
US3428025A (en) Xerographic development apparatus
US3611992A (en) Cleanup electrode
DE1278244B (de) Verfahren und Vorrichtung zur Entwicklung eines Ladungsbildes
US3638610A (en) Development apparatus
GB948916A (en) Improvements in or relating to the fusing of patterns of fusible particles on a support
US3685488A (en) Xerographic development
US3666518A (en) Development means and methods for developing electrostatic images