U.S. patent number 3,687,539 [Application Number 05/157,862] was granted by the patent office on 1972-08-29 for electrophotographic apparatus.
This patent grant is currently assigned to Katsuragawa Denki Kabushiki Kaisha. Invention is credited to Masayoshi Furuichi.
United States Patent |
3,687,539 |
Furuichi |
August 29, 1972 |
ELECTROPHOTOGRAPHIC APPARATUS
Abstract
In electrophotographic apparatus of the type comprising a rotary
photosensitive element, a corona discharge unit for depositing a
charge on the surface of the photosensitive element and an optical
system for projecting an information containing light image through
the corona discharge unit so as to form a latent image, the corona
discharge unit and the optical system are rotated in unison about
the rotary photosensitive element in a direction opposite to the
direction of the rotation of the photosensitive element. The
transfer printing device comprises means for bending the leading
edge of a recording paper into a V shaped configuration, means for
urging the recording paper against the rotary photosensitive
element to transfer print a powder image onto the recording paper,
a perforated suction cylinder to peel off the recording paper from
the photosensitive element after transfer printing and means for
admitting fluid under pressure into the space between the V shaped
leading edge of the recording paper and the photosensitive element,
and the cleaning device comprises a rotary brush in contact with
the surface of the photosensitive element, a rotary hollow cylinder
supporting the brush and provided with a plurality of perforations
for supplying in from the interior of the cylinder to the brush, a
stationary partition wall positioned in the hollow cylinder for
dividing the interior thereof into two longitudinal compartments, a
pair of corona discharge units of the opposite polarities disposed
in respective compartments for ionizing the air therein, and means
for supplying air under pressure into the compartments to discharge
the ionized air toward the brush.
Inventors: |
Furuichi; Masayoshi (Tokyo,
JA) |
Assignee: |
Katsuragawa Denki Kabushiki
Kaisha (Tokyo-to, JA)
|
Family
ID: |
27296130 |
Appl.
No.: |
05/157,862 |
Filed: |
June 29, 1971 |
Foreign Application Priority Data
|
|
|
|
|
Jun 30, 1970 [JA] |
|
|
45/57067 |
Jun 30, 1970 [JA] |
|
|
45/57068 |
Jul 27, 1970 [JA] |
|
|
45/65655 |
|
Current U.S.
Class: |
399/153; 399/353;
355/47; 271/900 |
Current CPC
Class: |
G03G
21/0035 (20130101); G03G 15/30 (20130101); Y10S
271/90 (20130101); G03G 2221/0005 (20130101) |
Current International
Class: |
G03G
21/00 (20060101); G03G 15/30 (20060101); G03G
15/00 (20060101); G03g 015/02 (); G03g
015/04 () |
Field of
Search: |
;355/3,8,47 ;96/1,1.4
;340/173PP ;118/637 ;250/49.52C |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3536483 |
October 1970 |
Watanabe et al. |
3540806 |
November 1970 |
Starkweather |
|
Primary Examiner: Matthews; Samuel S.
Assistant Examiner: Greiner; Robert P.
Claims
I claim:
1. In electrophotographic apparatus of the type comprising a rotary
drum, a photosensitive element carried by said rotary drum, a
corona discharge unit for depositing an electric charge on the
surface of said photosensitive element and an optical system for
projecting an information containing light image upon said
photosensitive element through said corona discharge unit so as to
form a latent image, the improvement which comprises means for
rotating in unison said corona discharge unit and said optical
system about the axis of said rotary drum in a direction opposite
to the direction of rotation of said rotary drum during operation
of said corona discharge unit.
2. The electrophotographic apparatus according to claim 1 which
further comprises a stationary corona discharge unit which is
operated prior to the operation of said movable corona discharge
unit to deposite a charge of a polarity opposite to that deposited
by said movable corona discharge device.
3. The electrophotographic apparatus according to claim 1 wherein a
hollow cylinder extending in the radial direction of said rotary
drum is provided between said photosensitive element and a
stationary object, said movable corona discharge unit is mounted on
the inner end of said hollow tube and said optical system is
mounted at a point intermediate the opposite ends of said hollow
tube.
4. The electrophotographic apparatus according to claim 3 wherein
said hollow tube is rotated about the axis of said rotary drum at a
speed corresponding to the power of magnification or reduction.
5. The electrophotographic apparatus according to claim 2 wherein
said photosensitive element comprises a photoconductive layer
exhibiting persistent internal polarization, a highly insulative
layer bonded to one side of said photoconductive layer and an
electrode layer bonded to the opposite side of said photoconductive
layer, said photosensitive element being mounted on said rotary
drum with said highly insulative layer faced outward.
6. The electrophotographic apparatus according to claim 3 wherein
said hollow tube carries a lamp for illuminating said object.
Description
BACKGROUND OF THE INVENTION
This invention relates to electrographic apparatus.
In one type of electrophotographic copying apparatus there are
provided a rotary photosensitive element carried by a rotary drum,
at least one corona discharge unit for depositing a charge of a
given polarity on the photosensitive element and a rotary mirror
for scanning an object and projecting the light image thereof onto
the photosensitive element through a lens. There are also used one
or more stationary reflecting mirrors so as to reflect the light
image several times. Such as arrangement increases the space
occupied by the optical system and often projects the light image
obliquely to the surface of the photosensitive element.
In the ordinary electrophotographic apparatus the latent image is
developed by a developer powder to form a powder image and the
powder image is transfer printed onto a recording paper which is
removed from the surface of the photosensitive element. However,
since the developer powder is ordinarily charged positively or
negatively and since a corona discharge unit is often used to
enhance transfer printing, the separation of the recording paper
after transfer printing is rather difficult owing to the
electrostatic attractive force due to the charges. A similar
problem occurs in the cleaning device. More particularly, the
developer powder remaining on the surface of the photosensitive
element after transfer printing is ordinarily removed by a rotary
brush. However, during the operation of the rotary brush the
removed developer powder gradually accumulates on the brush due to
the electrostatic force thus rendering it ineffective. Thus, it is
necessary to constantly remove the developer powder from the brush
to maintain it clean state.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a new and improved
combination of a corona discharge unit and an optical system which
does not increase the space necessary for these elements and can
project a light image always normally to the surface of a rotary
photosensitive element.
Another object of this invention is to provide an improved transfer
printing device capable of readily peeling off the recording paper
from the photosensitive element after transfer printing.
Still another object of this invention is to provide an improved
cleaning device by which the rotary brush thereof is maintained
clean.
According to one aspect of this invention, in electrophotographic
apparatus of the type comprising a rotary drum, a photosensitive
element carried by the rotary drum, a corona discharge unit for
depositing an electric charge on the surface of the photosensitive
element and an optical system for projecting an information
containing light image upon the photosensitive element through the
corona discharge unit, so as to form a latent image, the corona
discharge unit and the optical system are rotated in unison about
the axis of the rotary drum in a direction opposite to the
direction of rotation of the rotary drum during operation of the
corona discharge unit.
According to another aspect of this invention there is provided an
improved transfer printing divice which comprises means for feeding
a recording paper toward a rotary photosensitive element, means for
bending the leading edge of the recording paper into a V shaped
configuration, means for urging the recording paper against the
rotary photosensitive element to transfer print a powder image onto
the recording paper, a perforated suction cylinder positioned close
to the periphery of rotary photosensitive element to peel off the
recording paper therefrom after transfer printing and means for
admitting fluid under pressure into the space between the V shaped
leading edge of the recording paper and the photosensitive
element.
According to further aspect of the invention there is provided an
improved cleaning device for removing a developer powder remaining
on the surface of a rotary photosensitive element after transfer
printing, said cleaning device comprising a rotary brush in contact
with the surface of the photosensitive element, a rotary hollow
cylinder supporting the brush, the hollow cylinder having a
plurality of perforations for supplying air from the interior
thereof to the brush, a stationary partition wall positioned in the
hollow cylinder for dividing the interior thereof into two
longitudinal compartments, a pair of corona discharge units of the
opposite polarities disposed in respective compartments for
ionizing the air therein, and means for supplying air under
pressure into the compartments to discharge the ionized air toward
the brush.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a diagrammatic side view of electrophotographic apparatus
utilizing a rotary corona discharge unit and an optical system
constructed according to the teaching of this invention;
FIG. 2 shows the detail of the improved transfer printing apparatus
embodying the invention;
FIG. 3 is a plan view of the suction drum of the transfer printing
device shown in FIG. 2; and
FIG. 4 shows a cross-section of a cleaning device and a portion of
a rotary photosensitive element.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A preferred embodiment shown in FIG. 1 comprises a rotary drum 10
mounted on a rotary shaft 11 and carrying a photosensitive element
12 which may be any well known construction. However, in order to
form a latent image by the method disclosed in U.S. PAT. Nos.
3,457,070 and 3,536,483, the photosensitive element comprises a
photoconductive layer exhibiting persistent internal polarization,
a transparent highly insulative layer bonded to one surface of the
photoconductive layer and an electrode layer bonded to the opposite
side of the photoconductive layer. The photosensitive element is
wrapped about the periphery of the rotary cylinder with the highly
insulative layer faced outside. As above described, according to
the method disclosed in said patents, the latent image is formed on
the surface of the highly insulative layer by the steps of applying
a first electric field of one polarity by means of a first corona
discharge unit across the photosensitive element, and applying a
second electric field of the opposite polarity across the
photosensitive element by means of a second corona discharge unit
concurrently with the projection of an information containing light
image upon the photosensitive layer through the second corona
discharge unit. In FIG. 1, numeral 14 designates the first corona
discharge unit, and 15 the second corona discharge unit. An object
to be copies 16 such as a manuscript is mounted on the inner side
of a glass cylinder 17 concentric with drum 10 and illuminated by
lamps 18. According to the method described above while drum 10 is
rotated in the direction of arrow A, the object 16 is moved in the
direction of arrow C at a speed synchronous with the pheripheral
speed of drum 10 to project the light image of the object upon the
photosensitive element through a lens 19 and the second corona
discharge unit 15.
However, according to this invention, the object is held stationary
and the second corona discharge unit 15 and lens 19 are rotated in
the direction of arrow B or in the direction opposite to that of
the rotation of the drum 10. For this purpose, the second corona
discharge unit 15 is secured to the lower end of a hollow tube 20
extending in the radial direction of the rotary drum and the lens
19 is mounted at an intermediate point of tube 20. Although in the
illustrated example, lamps 18 are mounted on the upper end of tube
20, they may be held stationary. The tube 20 may be interlocked
with shaft 11 so as to be rotated at a given speed for a
predetermined angle by means of a suitable gearing, belt or another
transmission mechanism, not shown. Upon completion of the scanning
operation, the tube 20 is returned quickly to the original position
shown in FIG. 1 as shown by arrow C. The ratio of the scanning
speed and the peripheral speed of drum 10 is determined dependent
upon the power of magnification or reduction. For example, in the
case of a unity magnifying power the speed ratio is 1 : 1. Likewise
the position of the lens 19 along the axis of the tube varies
dependent upon the power of magnification or reduction. With this
arrangement, the light beam impinges upon the photosensitive
element always at right angles to the surface thereof so that off
focusing can be avoided. Use of a lens of a short focal length
decreases the length of the tube 20 thus decreasing the dimension
of the electrophotographic apparatus.
Where the photoconductor of the photosensitive element contains a
large number of deep charge trap levels such as a phosphor, a lamp
21 may be provided to irradiate the latent image formed on the
surface of the highly insulative layer to increase the contrast of
the reproduced image as fully discussed in U.S. Patent No.
3,457,070.
The latent image if then developed by a developing device 22 of any
well known suitable type to form a powder image and the powder
image is transfer printed onto a recording medium by a transfer
printing device 23. The developing powder remaining on the surface
of the photosensitive element after transfer printing is removed by
a cleaning device 24 for preparing the photosensitive element to
the next cycle. Although not shown in the drawing, an AC field is
applied across the photosensitive element for completely depolizing
the element before re-use.
The invention further contemplates the provision of an improved
transfer printing device including an improved paper peel-off
device as shown in FIGS. 2 and 3.
More particularly, as shown in FIG. 2, the transfer printing device
23 comprises a suction drum 30 positioned close to the periphery of
the photosensitive element 12 carried by rotary drum 10 and a press
31 positioned on the entry side of the transfer printing device for
bending the leading edge of a recording paper 32 into a letter V
shaped configuration as shown by a reference numeral 33. The press
31 comprises a stationary upper mould 34 and a movable lower mould
35 which is operated by an electromagnet 36 through a lever 37
pivoted at 38. The lever 36 is normally held in the position shown
by means of a return spring 39. When the leading edge of the
recording paper appears at the exit of a shute 36 it is detected by
suitable means such as a micro-switch or a photoelectric cell (not
shown) which energizes the electromagnet 36. As a result, the
leading edge is bent into a V shaped configuration by the
co-operation of upper and lower moulds 34 and 35. As the leading
edge of the recording paper comes into contact with the periphery
of the photosensitive element a roller 40 is moved upwardly from
the dotted line position to the solid line position to urge the
recording paper against the periphery of the photosensitive
element. The powder image is then transfer printed onto the
recording paper by the contact pressure between roller 40 and the
photosensitive element. If desired, a third corona discharge unit
41 may be provided for improving the transfer printing in a manner
well known in the art. The charge deposited by the third corona
discharge unit attracts the paper to the photosensitive element.
However, the bent portion 33 still maintains its configuration
during transfer printing.
The suction drum 30 comprises an inner cylinder 42 with one side
close to the photosensitive element opened as at 43 and an outer
cylinder 44 with a number of perforations 45. The interior of the
inner cylinder 42 is communicated with a suction device, not shown,
to attract the recording paper onto the periphery of the outer
cylinder 44 at the opening 43. As shown in FIG. 3, the outer
cylinder 44 is formed with a plurality of parallel spaced apart
circumferential grooves 46 and perforations 45 and is rotated about
the inner cylinder 42 by an electric motor, not shown. A plurality
of stripping members 47 are received in respective grooves 46 in
the tangential direction with respect to the periphery of the outer
cylinder. Accordingly, when the paper is advanced to the position
of opening 43, the paper will be attracted onto the outer cylinder
by the suction applied through perforations 45. An air nozzle 48 is
provided to direct compressed air in the transverse direction of
the drum 10 to admit air to the inside of the bent leading edge
thus peeling off it away from the photosensitive element. The paper
is then transferred to a heated fixing device, not shown.
In this manner, the bent portion 33 of the recording paper does not
adhere to the periphery of the photoconductive element during
transfer printing so that the compressed air admitted into the
space between the bent portion and the photosensitive element
enhances the separation of the recording paper. Of course the
operation of forming the latent image and the feed of the recording
paper are suitably synchronized so as to anoide transfer printing
of the latent image upon the bent up portion. Thus, the invention
is especially suitable for recording papers of relatively large
width.
Another feature of the invention lies in the provision of an
improved cleaning device. As shown in FIG. 4, the cleaning device
24 comprises a rotary brush 50 which is rotated in the direction of
an arrow to remove a developer or toner powder 51 remaining on the
surface of the photosensitive element after transfer printing. The
removed powder is discharged to the outside through an exhaust duct
52 having a base surrounding the brush. The rotary brush 50
includes a hollow cylinder 53 with a plurality of small
perforations 54, and an air permeable cloth 55 surrounding cylinder
53 and implanted with bristles 56. Bristles 56 and cloth 55 may be
replaced with an animal fur. The interior of the hollow cylinder 53
is divided into two longitudinal compartments 57 and 58 by a
longitudinal partition wall 59 of any desired configuration. Corona
discharge units 60 and 61 are disposed in compartments 57 and 58,
respectively. The hollow cylinder 53 and bristles 56 are rotated
whereas partition wall 59 and corona discharge units 60 and 61 are
held stationary. One end of the cylinder 53 is closed and air under
pressure is admitted into the opposite end by a suitable fan, not
shown. The polarity of corona discharge unit 60 is selected to
enhance removal of developer powder 51 away from the photosensitive
element whereas that of corona discharge element to enhance removal
of the powder away from the bristle. The air in compartment 57 is
ionized by corona discharge unit 60 and is then discharged to the
out side of cylinder 53 through perforations 54 as shown by solid
line arrows whereas the air in compartment 58 is ionized by corona
discharge unit 61 (opposite polarity to corona discharge unit 60)
and is then discharged outwardly as shown by dotted line
arrows.
When brush 50 is rotated with a predetermined contact pressure to
the photosensitive element 12 the remaining developer powder 51 is
swept away and attracted by bristle 56. Since the air ionized to
one polarity by corona discharge unit 60 fills the interstices
between the bristles, the remaining powder can be readily removed
from the surface of the photosensitive element. As the brush is
rotated further, the powder collected by the bristle is readily
separated therefrom by the air ionized to the opposite polarity by
corona discharge unit 61. The separated powder is exhausted to the
outside together with the air.
By the action of two corona discharge units of the opposite
polarities, not only the powder remaining on the photosensitive
element can be readily removed, but also the powder collected by
the brush can be readily removed.
* * * * *