US3609484A - Safety device for charging device of electrophotographic apparatus - Google Patents

Safety device for charging device of electrophotographic apparatus Download PDF

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Publication number
US3609484A
US3609484A US43820A US3609484DA US3609484A US 3609484 A US3609484 A US 3609484A US 43820 A US43820 A US 43820A US 3609484D A US3609484D A US 3609484DA US 3609484 A US3609484 A US 3609484A
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US
United States
Prior art keywords
corona discharge
wire
retaining member
charging device
discharge wire
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
US43820A
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English (en)
Inventor
Hisashi Sakamaki
Yoshimasa Kimura
Osamu Sawamura
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.)
Canon Inc
Original Assignee
Canon Inc
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 Canon Inc filed Critical Canon Inc
Application granted granted Critical
Publication of US3609484A publication Critical patent/US3609484A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • 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
    • G03G15/02—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices
    • G03G15/0291—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices corona discharge devices, e.g. wires, pointed electrodes, means for cleaning the corona discharge device

Definitions

  • the present invention relates to a charging device for use in eleetrophotographic apparatus and more particularly to a charging device of the type described above provided with a safety device simple in construction and reliable in prevention of an accident or damage caused by the breakage of a discharge wire.
  • a surface of an electrophotographic photosensitive member having a photoconductive layer must be uniformly imparted with a predetermined magnitude of electrostatic charge.
  • a charging device a discharger
  • a corona discharge wire made of tungsten or stainless steel of about 0.1 mm. in diameter and in opposed relation with the surface of the photosensitive member.
  • a high voltage is applied across an electrode upon which is placed the photosensitive member and the corona discharge wire, thereby producing the corona discharge so as to impart the electrostatic charge to the surface of the photosensitive member.
  • the corona discharge wire Since a high voltage is applied, the corona discharge wire is gradually corroded and deteriorated so that the tensile strength of the wire is so reduced as to cause the breakage. Furthermore, when the toner or the like is attached to the corona discharge wire, the corona discharge tends to be concentrated at one portion so that a spark discharge is produced, thereby causing the breakage of the wire. In some cases, the copying paper is wrapped around the charging device and brought into contact with the corona discharge wire, thus resulting in the breakage. In this case, between the photosensitive member and the broken wire the spark is produced so that not only the photosensitive member but also the charging device are damaged. In the worst case, the electrophotographic apparatus itself is damaged and an operator may suffer electric shock.
  • the discharge cannot be produced efficiently at a relatively low voltage unless the diameter of the corona discharge wire is made smaller (generally 0.0. to 0.08 mm.). Therefore, greater tension may not be applied to the wire because breakage will occur at once. Thus, fabrication has been difficult.
  • the primary object of the present invention is to provide a charging device having a safety device so as to prevent accident or damage when the breakage of a corona discharge discharge wire occurs.
  • Another object of the present invention is to provide a charging device having a safety device capable of interrupting immediately the high voltage current flow through a corona discharge wire when the breakage thereof occurs.
  • a further object of the present invention is to provide a charging device having a safety device of the type which when the breakage of a corona discharge wire occurs, the high voltage to the wire is immediately grounded, thereby interrupting the high voltage to the wire.
  • FIG. I is a front view of a charging device for electrophotographic apparatus embodying the present invention in one form
  • FIG. 2 is an electric circuit diagram of the device shown in FIG. 1;
  • FIG. 3 is a graphical diagram of the voltage-current characteristic curve of a constant voltage transformer.
  • FIG. 4A and 4B are fragmentary front views each illustrating the relationship between a short-circuit electrode and a corona discharge wire retaining member in accordance with the present invention.
  • corona discharge wires 2 are enclosed in a conductive shielding frame body I, made of, for example, stainless steel, aluminum, etc.
  • the corona discharge wires have a uniform, suitable diameter and are made of noncorrosive materials such as stainless steels.
  • Both ends of the corona discharge wires 2 are fixed to elastic retaining members 3, and 3 made of electrically conductive material.
  • elastic retaining member 3 instead of the elastic retaining member 3 a nonelastic retaining member may be utilized.
  • the retaining members 3, and 3 are in turn securely fixed to insulating sidewalls 4, and 4 at both ends of the shielding frame body 1.
  • Short circuit electrodes 5 which are fixed to the insulating sidewall are grounded and the charging device is provided with a cord for connection with an electric power source.
  • the corona discharge wires 2 are deteriorated by the corona discharge and broken by spark discharges, wrapping of copying papers or for other reasons.
  • the spark discharge occurs therebetween so that the inflammable substance starts to burn, thus causing a tire.
  • the broken corona discharge wires 2 are in contact with a metallic part, it may cause an electric shock to an operator.
  • FIG. 4A shows another embodiment of the present invention in which a pair of retaining members are mounted on a support 8.
  • the retaining members have no elasticity, so that the retaining members on which the respective corona discharge wire is suspended at each end thereof are urged to the sidewall 4, of the shielding frame body 1 by respective tension springs 9 and 10 which have suitable tensile strength.
  • FIG. 4B shows another embodiment of the present invention in which a single retaining member 3 is pivoted.
  • the corona discharge wires suspended on both ends of the retaining member 3 are balanced in respect to each other in the normal condition.
  • one discharge wire is broken, one end of the retaining member 3 is brought into contact with a short circuit electrode 5 by tensile force of the other discharge wire.
  • a very reliable safeguarding may be attained only by the provision of the short circuit electrode 5 in opposed relation with the wire retaining member 3.
  • the safety device of the present invention may dispense with a switch, lead wires, etc. which are required in the conventional device. Furthermore, only small tension is required to extend the corona discharge wires 2 because it is sufficient to space the retaining electrode 3 from the short circuit electrode 5 by a very small distance.
  • a charging device for use in an electrophotographic apparatus comprising at least one corona discharge wire,
  • At least one short circuit electrode disposed adjacent to the end of said corona discharge wire on the side of application of high voltage thereto
  • a cord connectable to an electric power source for applying the high voltage to said corona discharge wire.
  • said corona discharge wire retaining member has a fulcrum point and said wire retaining member is pivoted to retain the corona discharge wires on both sides of said fulcrum point, and at least two short circuit electrodes are disposed adjacent to the free ends of said wire retaining member.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Physics & Mathematics (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
US43820A 1969-06-09 1970-06-05 Safety device for charging device of electrophotographic apparatus Expired - Lifetime US3609484A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1969053157U JPS4839623Y1 (de) 1969-06-09 1969-06-09

Publications (1)

Publication Number Publication Date
US3609484A true US3609484A (en) 1971-09-28

Family

ID=12934996

Family Applications (1)

Application Number Title Priority Date Filing Date
US43820A Expired - Lifetime US3609484A (en) 1969-06-09 1970-06-05 Safety device for charging device of electrophotographic apparatus

Country Status (4)

Country Link
US (1) US3609484A (de)
JP (1) JPS4839623Y1 (de)
DE (2) DE2028143C3 (de)
GB (1) GB1316785A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3980929A (en) * 1975-07-07 1976-09-14 Xerox Corporation Corona current interrupter
US4551784A (en) * 1984-06-29 1985-11-05 Xerox Corporation Corona generating device
US5627376A (en) * 1995-09-08 1997-05-06 Samsung Electronics Co., Ltd. Wire corona charging apparatus

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3980929A (en) * 1975-07-07 1976-09-14 Xerox Corporation Corona current interrupter
US4551784A (en) * 1984-06-29 1985-11-05 Xerox Corporation Corona generating device
US5627376A (en) * 1995-09-08 1997-05-06 Samsung Electronics Co., Ltd. Wire corona charging apparatus

Also Published As

Publication number Publication date
JPS4839623Y1 (de) 1973-11-21
GB1316785A (en) 1973-05-16
DE7021444U (de) 1974-11-07
DE2028143A1 (de) 1971-01-21
DE2028143B2 (de) 1973-05-10
DE2028143C3 (de) 1973-11-22

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