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Патент USA US3028809

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April 10, 1962
Filed March 8, 1957
2 Sheets-Sheet 1
i5» 1'
Fag. Z
April 10, 1962
Filed March 8, 1957
2 Sheets-Sheet 2
3.7g. 3
United States atent
Patented Apr. I 10,’. 1 962
wherein a surface means bearing a permanent image is
placed against one surface of a transparent electret and
Daniel Franklin Keller, 525 Sheridan Road, Kenilworth,
light radiation projected through the surface means and
electret wherein a latent image is formed on a photo
conductive coating on the opposite surface of the electret.
Ill., and Harry E. Gunning, Hazel Crest, Ill., assiguors,
image is rendered visible by applying a dusting pow
by mesne assignments, to Daniel Franklin Keller, Ken
der and this image is transferred by a surface having an
ilworth, Ill.
a?inity for the powder and carried to an electret having
Filed Mar. 8, 1957, Ser. No. 644,754
a polarity opposed to the polarity of the ?rst electret
16 Claims. (Cl. 95—1.7)
10 surface whereby the image will be attracted to a paper
This application is a continuation-in-part of our co
placed‘between the transfer surface and the second elec_
pending application Serial No. 590,621, ?led June 11,
1956, now US. PatentNo. 3,000,735 issued September
Another feature of the invention lies in the provision
19, 1961.
of a method and apparatus for utilization in a camera
This invention relates generally to electrophotography 15 wherein a photoconductive layer is utilized as a surface
and electrophotograhic printing and, more particularly,
bearing a latent charge image and succeedingly vpassd
to improved methods and apparatus for producing latent
over ends of an electret or" opposite polarity and there
charge images on surface means suitable for use in printing
after positioned against a grounding plate and exposed
and reproduction procedures, for example, by electropho
to radiation from an image and the image is subsequently
?xed on the photoconductive surface by passing it through
tographic means.
By exposing photoemissive or photoconductive layers
or surfaces to radiation having a desired image or pattern,
a dusting chamber. The surface bearing means is sub
‘ sequently passed through a spray chamber wherein the
there is produced a corresponding emission of electrons
dust is ?xed to the surface in the shape and density varia
in the areas receiving the radiation whereupon an elec
tions representing the image.
trostatic latent image is produced. The electric charge “
A further feature of the invention is the provision of
pattern which forms the electrostatic latent image may
‘a printing method and mechanism wherein a surface hear
be rendered visible by various developing procedures, for
ing an image is placed against a surface of an electret and
example, by depositing a suitable material such as ?nely
a photosensitive insulating material on thin plastic is
divided particles which come under the in?uence of the
placed over the surface and exposed to a light and subse
charge pattern.
quently passed to a dust chamber. The plastic material
In following the procedures outlined heretofore, it has
been necessary to utilize bulky equipment oftentimes ne
with the photoconductive insulating surface is subsequent
ly exposed'to another light and carried against a copy
cessitating the use of high voltage generating equipment.
material held against an electret surface having an outer
Artisans in the field have been confronted with serious 35 surface of opposite polarity from the surface beneath the
problems with respect to the uniformity of a charging
surface bearing the image whereby dust which has been
?eld, the lack of ?exibility with respect to the size of the
images reproduced and the safety factors which are present
in connection with the high voltage equipment employed.
Further, methods heretofore used have not been adapt
able to, utilization in an apparatus of a size and weight
and having simplicity to be used as a camera or to be
_ used in a printing system. In accordance with the prin
placed on the surface of the plastic material in accordance
with the density of the image is transferred to the copy
material producing a printed copy of the image.
It is, therefore, an object of the present invention to
provide an electrophotographic method and apparatus
wherein a strip of supporting material coated with a
photoconductive insulator may be fed through a camera
ciples of the present invention, it is contemplated to pro
to produce a latent charge image by an electrophotographic
vide methods and apparatus which may be adapted and 45 process conducted entirely within the camera.
utilized in a camera suitable for practical usage for di
Another object of the invention is to provide a mecha
rectly producing a reproducible, or developed, or per
nism wherein a permanent image is produced Within a
manent image by electrophotographic means. The present '
camera by drawing a clear plastic ?lm coated with a
invention also contemplates the provision of methods and
photoconductive insulating material over an electret and
apparatus which may be utilized in a relatively uncom- ,
exposing the ?lm to radiation and subsequently drawing
plicated printing arrangement wherein copies or prints
are rapidly and directly made from the permanent image
with the utilization of electrophotographic processes.
to develop and ?x the ?lm.
Another object of the invention is to provide a camera
In accordance with the principles of the present inven
tion, it is contemplated to provide as a charging means
in an electrophotographic process a layer formed from
an electrically stressed substance and providing an eifec~
tive working surface which exhibits a permanent elec
trostatic ?eld as high as 30,000 volts per centimeter. A
layered member so provided is sometimes referred to in
the electrostatic arts as an “electret.”
A feature of the present invention is to provide a
the ?lm through a dust chamber and a spray chamber
wherein a ?lm coated with a photosensitive layer is se
quentially drawn over surfaces of opposite polarity on the
electret and thereafter placed against a ground plate and
exposed to the radiation of an image and substantially
drawn through a dust chamber and spray chamber to de
velop and ?x the image on the ?lm.
Another object of the invention is to provide an im
proved photoelectric printing method and apparatus which
is simple in construction and operation and wherein copies
camera wherein the light radiation passing through the
or prints 'may be directly and continuously made by a
lens falls upon a photoconductive strip backed by an
electret and wherein the strip is subsequently drawn
through a dusting chamber and thereafter through a ?xing
chamber so that the dust which is gathered upon the sur
face in the form of the image will be permanently ?xed
photoelectric process obviating the necessity of providing
permanent images by 'an electrophotograpln'c process
‘Another object is to provide another form of mecha
expensive and complex equipment such as has hereto
fore been necessary.
Another object of the invention is to provide an elec
trophotographic printing process which ?nds utility in a
to the strip of material.
printing mechanism wherein a powder deposited in the
It is another feature of the invention to provide a 70 form of an image is carried by a transfer blanket to a
method and apparatus for the printing of copies from
, printing paper.
nism wherein the powder may be transferred directly to,
tem 20 maybe opened for a predetermined period of
a printing paper and ?xed thereon.
Other objects and advantages will become more ap
parent in the teachings of the principles and features of
the invention with the disclosure of the preferred embodi
ments thereof in the speci?cation, claims and drawings,
in which:
FIGURE 1 is a somewhat schematic vertical sectional
view of one form of a camera employing the principles
time to permit the passage of light radiation through the
lens in accordance with the re?ective properties of the
image to be photographed.
At the focal point of the lens is a re?ector plate 22
which is set at a 45° angle with the camera shown in the
horizontal position, so that the image is re?ected upward
ly against a supporting surface adapted to have a latent
charge image formed thereon, sometimes referred to
10 herein as a ?lm ‘24.
of the invention;
The ?lm may conveniently comprise av backing or
FIGURE 2 is another vertical sectional view taken
carrying layer with a layer of photo-conductive material
through the camera and showing schematically another
thereon such as sulfur, anthracene or mercuric sul?de.
form of the camera;
Means for supplying the ?lm are shown in the form of a
FIGURE 3 is a vertical sectional view shown in sche
matic form of a printing mechanism for making copies 15 supply roll 26 from which the ?lm is threaded to be posi
tioned against the ground plate 28 in the picture taking
or prints of images; and
location. The end of the ?lm next passes through a
FIGURE 4 is avertical sectional view shown in sche
dusting chamber 38 and then passes into a spraying
matic form of another arrangement of a printing mecha
chamber 40.
In the embodiments of FIGURES 1 and 2, the inven 20 The spraying chamber is provided with a hinged door
42 which may be swung open about its supporting hinge
tion is shown using an electret in a box or similar hand
4+4 to remove the developed and ?xed end of the ?lm
camera for purposes of making permanent images.
As used herein, the term “electret” denotes a permanent
at 46.
1y electri?ed substance exhibiting electrical charges of
In advancing the ?lm into the camera, the ?lm is ?rst
opposite sign at its extremities and of the type disclosed 25 drawn over a scanning bar or roller 48 positioned to be
in our acknowledged co-pending application.
in engagement with the ?lm. The scanning bar 48 is of
Electrets are made from solid substances which are
a polarity determined by electret 50.
capable of being melted without chemical decomposition
The electret member 50 comprises a body 52 with a
and which possess a ?nite dipole movement in liquid
?rst lower surace 54 and a second upper surface 56. The
state, for example, carnauba wax-beeswax mixtures, mix 30 surfaces 54 and 56 are spaced from each other and paral
lel and exhibit a permanent electrical charge with the sur~
tures of carnauba wax with various synthetic, thermo
faces 54 and 56 being of opposed polarity in accordance
plastic or polar resin such as polyvinyl chloride polymers,
with the de?nition of theterm “electret.”
etc., soda-lime glass, Pyrex glasses, quartz, and sulfur.
As illustrated in FIGURE 1; the electret 50 is pro
A, permanent charge is imposed upon the substance of
vided on the surface 54 with an electrically conductive
the electret by allowing the liquid electret-forming sub
layer 58. The surface 56 is provided with an electrically
stance to solidify in a strong electric ?eld. For example,
conductive layer 60.
the substance may be melted while interposed between
Attached to the ?rst electrically conductive layer 58
two electrically-independent tinfoil electrodes attached
to opposite poles of a high voltage D.C. source furnish 40 is an electrical lead 61 which is electrically connected to
the scanning bar 48 so as to place a charge on the sur
ing a DC. ?eld of not less than 10,000 volts per centimeter.
face of the coated paper in accordance with ‘the electro~
The liquid substance is allowed to remain in the ?uid
static charge on the surface 54 of the electret.
state within the ?eld for at least one hour and is,‘ there
As the ?lm 24 is drawn forwardly to an image-forming
afterhprogressively cooled at a slow rate within the ?eld
location 62, it passes over the electrically conductive suruntil completely solidi?ed.
It has been found that electrets so formed are per 45 face 56 which places a charge on the surface of the photo
conductive coating in accordance with the electrostatic
manently volume~polarized and possess permanent elec
charge on the surface 56 of the electret.
trostatic ?elds of opposite polarities at the extremities or
When the ?lm is in the image-forming location 62, it
surfaces thereof to which the electrodes were attached.
is positioned in juxtaposed relationship to the ground .'
In the electrophotographic processes of the prior art,
charges in the range of 4500 to 6000 volts per centimeter 50 plate 28.
The light-conducting ?lm has been in location to re
have been utilized, The permanent electrostatic ?elds
ceive light radiations of the image. As the shutter sys
possessed by electrets may range from a few hundred volts
tem 2.0 is opened, the ?lm 24 is exposed to radiation and
per centimeter and may exceed as high as 30,000 volts
surface electrons are discharged to the ground plate 28
per centimeter at the working surfaces of the electret and,
accordingly, it is contemplated according to the principles 55 in the shape and density of the image.
of the present invention that the electret will be provided
with surfaces exhibiting a permanent electrostatic ?eld
in the order of magnitude of a few hundred volts to an
The ?lm 24 is next rolled forward to pass through the
dusting chamber 38. The dusting chamber exposes the
photoconductive surface to ?ne pigment particles and
these particles are picked up in the shape and density
upper limit determined by the breakdown potential of
of the image.
the air in contiguity to the charged surface.
Guide pins 41 or the like may be provided to guide
Although the principles of the present invention ?nd
the ?lm as it passes with its surfaces 43 exposed to the
speci?c utility in the embodiments illustrated and de
dusting chamber 38. The dusting chamber 38 may be
scribed, it will be understood that the features and ad
provided with seals at its edges to avoid the escape of
vantages of the invention may be utilized in other en
dust down into the camera chamber 14 or up into the
vironments and the speci?c forms shown are for purposes 765
of illustration and for purposes of disclosing the preferred
As illustrated in FIGURE 1, a camera is illustrated
spray chamber 40. The dust may be created by agita
tion means or may be applied by a brush similar to an
iron ?ling brush of the type known to the art.
After being developed, the dust coated ?lm is drawn
as having ‘a housing shown diagrammatically at 10 with 70 up into the spray chamber 40 where the image is ?xed.
ya bellows 12 or similar lightproof enclosure de?ning a
camera chamber ‘14. At the front of the camera cham
ber is a lens and shutter assembly 16 with lenses 18 and
a shutter system 20. The lens and shutter ‘arrangement
are the type known to the art whereby the shutter sys
The ?xing is accomplished by applying a spray such as
by nozzle 64 which sprays over the surface of- the‘ end
of the image and causes a permanent adherence of
the dust to the ?lm in the density and shape of the image.
A plastic solution spray such as F‘Krylon” or any solid
plastic dissolved in a volatile solvent, which solvent is
compatible with the ?lm material, may be applied to ?x
which extends the length of the cylinder to provide an
equal radiation of the length of the ?lm 122. The light
the image.
source can be at the axis, but is not limited to being at
In the form show in FIGURE 2, the camera is pro:
vided with a housing 66 having a lightproof bellows 6-8
forming a camera chamber 70. At the front of the cham
ber is located a lens and shutter assembly 72 carrying
lenses 74 with a shutter system 76. The assembly 72 is
arranged so that the shutter may ‘be opened for a pre
i that location. A light source can also be placed very near
to the inner surface of the electret at a point where the
image transfer to the photoconductive surface 116 is to
take place.
A light shield 128 is provided to restrict the light to
the required longitudinal area. As illustrated, the shield
determined length of time to permit light radiation corre 10 128 has a break or slit 130 along one side in order that the
sponding to the image to pass rearwardly within the
light rays may pass therethrough to pass through the trans
camera chamber 70. At the back of the camera in an
parent holder 124; the negative 122,~and the electret 114.
image-forming location 78 is the ?lm 80. The ?lm may
A grounding brush 132 is provided supported on a hold
be a backing paper with a photoconductive insulating
er 134 to be in brushing contact with the outer photo—
material ‘thereon and is preferably formed ‘of a roll of 15 conductive layer 116. ' The brush grounds the outer layer
clear plastic with a photoconductive insulating surface.
and removes stray charges which would create a false
'_ ,
The ?lm is supplied from a supply roll 82 housed in
‘ an upper portion‘ 184 of the housing 66 and feeds down
As the electret tube 114 rotates in a clockwise direction,
wardly to the image-forming location 78 and subsequently
as illustrated in FIG. 3, vthe outer photoconductive coat
. through a dust chamber 86 and a spray or ?xing cham 20 ing or surface 116 passes through a dusting-box 136. > The
ber 88.
In moving to the image-forming location 78, the ?lm
80 passes .a lateral ground brush 91. The ground brush
may be moved across the face of the ?lm along the guide
dusting box ‘exposes the photoconductivev surface 116,
which has had the latent image photoelectrically placed
thereon in passing the light exposure of, the slit 130, to a
?ne pigment dust. The dust is attracted to the coating
93 or it may be more feasible to position the ground to 25 118 in the form and density in accordance with the latent
contact the ?lm as it comes off the roll 82 as a ground
image on the ?lm.
on the face of the electret may bring charges to the sur
As the coated surface 118 carrying the image, made
visible by the attracted powder, leaves the dusting box 136
In the picture-taking location, the ?lm is backed by an
it is engaged by transfer cylinder 138 carrying a blanket
electret'90 which is shown in the form of a ?at plate 92 30 transfer surface 140. The transfer cylinder is geared to
having opposed parallel surfaces 94 and 96, which ex
the electret cylinder, in a drive not shown, so that where
hibit permanent electrostatic charges of opposing polarity.
their surfaces meet at a nip 142 they will have an equal
In the picture-taking location, the shutter system is
peripheral speed. It should also be understood that the
opened whereupon the ?lm 80 is exposed to radiation. A
transfer cylinder 13-8 and the electret cylinder 114 can be
latent electrostatic image is produced on the ?lm in the 35 conveniently made of the same diameter thereby insuring
con?guration and density of the image.
equal peripheral speeds.
After the image has been formed on the ?lm, it is
' The blanket or transfer surface 140 on the cylinder, is
rolled downwardly to pass into the dusting chamber 86.
of a nature that will have a greater affinity for the powder
In this chamber, the ?lm is exposed to a ?nely separated
or dust on the electret cylinder than the surface 118 of
pigment or dust which attaches itself to the surface in 40 the electret cylinder. The dust will thus be transferred
the con?guration and density of the image and changes
to the surface 140 of transfer cylinder remaining in the
the latent electrostatic image to a visible image. ‘The ?lm
form of the image. The dust or powder, which has been
portion 98, which is in the dust chamber 86, is guided by
transferred to the blanket surface 140 by contact and
spaced horizontally extending guiding bars 160'.
affinity, will now be transferred to the surface of a print
The leading end 102 of the ?lm is rolled forwardly 45 ing material such as paper 144. ‘The length of paper ‘144
into the spray or ?xing chamber 8-3. At this location a
is fed between the transfer roll 138 and a second electret
spray nozzle 104 is supplied from a manifold or con
146 at a location 148 where their peripheral surfaces sub
tainer 106 and sprays a material such as a clear plastic
stantially meet. The paper is rolled from a supply roll
coating to ?x the powdered material to the surface of
148 onto a take-up roll 150.
the ?lm end 102. The end 102 of the ?lm upon which V51)
The electret roll or cylinder 146 has anouter surface
the visible image has been ?xed, may be removed by
152 exhibiting a permanent electrostatic charge of a
swinging back a door 106 which is hinged to the back of
polarity opposite that of the outer surface 118 of the
the housing. by a hinge 108.
electret tube 114. Thus the powder forming the visible
FIGURE 3 illustrates another form of the method of
image, which is coated on the surface 140‘ of the transfer
the invention for printing copies from a permanent image
roll, is attracted to the electret roll 146 and coats on the
by an electrophotographic process. A housing is illus
trated at 112 wherein a hollow, cylindrically shaped or
image-receiving paper 144.
The blanket surface 140 of the transfer cylinder 138
tubular electret 114 is located to rotate about a horizontal
may be coated with a material such as rubber which has a
axis. The tubular electret is made of a transparent mate
greater a?inity for the powder image than the insulating
rial such as a clear plastic, glass or the like and the outer 60 surface 116 of the electret tube 114. In one form it is
surface 118 is coated with a photoconductive insulative
advisable to ground the surface‘ 116 of the electret to
material. The outer surface 118 of the electret, beneath
the coating 116, and the inner surface 120‘ are of op
expedite transfer of the image to the blanket 140. This
may be accomplished by embedding small particles of cop
posite polarity and are permanently electrostatically
per or similar substance into the blanket surface .140 of
charged in accordance with. the characteristics of the 65 the transfer, cylinder 138.
After the image has been transferred to the paper 144,
The ?lm 122 is to be placed inside the inner surface
it is carried upwardly on the surface of the paper to a
120 of the tubular electret 114. The ?lm 122 is held
?xing element 154 which may be in the form of a spray
, against the inner surface of the electret by means of clips
or vapor or a heating element.‘ As illustrated, the ?xing
“or similar holding devices that will retain it against the 70 element 154 provides a heating element 156 which ?xes
surface, but which are/not shown. As illustrated, the ?lm
the image to the paper 144.
is held to the inner surface 120 by a sheet of clear semi
In the form shown in FIGURE 4, a hollow electret tube
rigid plastic 124 which may be supported between rigid
1’ stops, not shown.
The inside of the tube contains a light source 126 75
' 160 is carried partially exposed in a housing 162 to-rotate
' about a horizontal axis. The electret has an outer surface
163 exhibiting a permanent electrostatic charge. ' '
In this form of the invention, the ?lm 164 is clamped to
an exterior image for a controlled period of time, an
the outer surface 163 of the electret cylinder tube 160.
The ?lm may be held to the surface by various means but
electret within the camera chamber having a surface face
may be pulled tightly thereto by a thin outer sheet of plas
surfaces each exhibiting permanently charged electro
tic material 166. This plastic material may be a material
such as “Mylar” polyester ?lm which is available com
static ?elds of opposite polarity, means at one side of said
electret supplying an area of image-forming ‘material with
a photoconductive layer thereon md adapted to be placed
ing the lens and including opposed coextensive parallel
over the electrostatically charged surface facing the lens,
The thin plastic sheet is clamped to the cylinder at
a movable grounding element adapted to be moved over
one end drawn tightly by appropriate clamps (not shown
in detail) at the other end, with the clamped ends being 10 the surface of the image-forming material whereby stray
charges on the surface thereof are discharged, and means
shown’ generally at 168.
for subjecting the image-forming area to contact with
The outer thin material 166 is dipped in a thin ‘solution
electrostatically attracted material to form a visible image
of photoconductive insulating material and is coated
on the surface of said image-forming material.
2. An electrophotographic camera combination com
The light source is shown at 170 and in this form 15
prising means forming a closed lightproof camera cham
is on the outside of the electret tube 160. The light
source may be placed within a housing 172 having a nan
her, a' lens positioned to expose the interior of the cham
row slit 174 across the front to expose‘the photoconduc
t-ive layer 166 of the ?lm 1164 to the light across an axially
ber to an aerial image, a shutter system for the lens '
extending area.
adapted to open the lens for a predetermined period of
20 time wherein light radiation enters the camera chamber, ,
A ground brush 176 is provided carried on a holder
177 to neutralize the outer plastic material and remove
a plate of permanently electrically pre-stressed substance
having parallel surfaces exhibiting permanently charged
electrostatic ?elds of opposite polarity ‘with one of said
surfaces facing the light radiation which enters the cam
When the photoconductive material 166 ‘has been car~
ried past the light source, it next passes through a dust 25 era chamber through the lens, means for movably supply
ing an image-forming strip of material having a photo
chamber 178. In the dust chamber 178, the surface of
‘conductive layer adjacent a second layer whereby radiation
‘the photoconductive material 166 is exposed to a ?ne dust
maybe projected through the lens onto said photoconduc
or pigment which is attracted to ‘the surface in the shape
tive layer while it is in proximate relationship to the sur
and density of the image to be printed.
stray electrostatic ?elds therefrom.‘
After the dust chamber, the continued ‘rotation of the
electret tube 160 exposes the photoconductive material
166 to alight source 180.
This light source brings a
charge to the entire surface.
In the form embodied in ‘FIGURE 4, the transfer roll
face of the electrically stressed plate, a stationary ground
bar located so that the moving image-forming strip will
pass in close proximity thereto to remove stray electro
static ?elds from the photoconductive surface thereof,
and means located adjacent the electrically pre-stressed
is omitted and the photoconductive layer 166 is next 35 plate providing an atmosphere of electrostatically at
tracted material whereby the surface of said image
pressed against a copy material such as a paper 182 fed
forming strip is coated with the material in a shape and
from a supply roll 184 and rolled onto a take-up roll 186.
density varying with the radiation received in accordance
The paper passes between the photoconductive layer 166
with the light emitting properties of the image, and means
and a paper electretroll 188. The paper electret roll has
an outer surface 190 which is opposite in polarity to the 40 for ?xing the layer of electrostatically attracted material
on the image-forming strip to render the image permanent.
outer vsurface 163 of the electret tube 160. This causes
3. In a mechanism for producing an image by an ‘elec
an attraction and a transfer of the visible image formed
trophotographic process comprising a closed lightproof
by the powder on the 'photoconductive material 166 to
camera chamber, an electret plate within said chamber
the paper 182.
The image, carried on the paper 182, next passes over 45 having opposed parallel spaced surfaces being charged
with a permanent strong electrostatic ?eld withropposit‘e
the image ?xing element 192. The ?xing element may
surface having opposite polarity, a lens for said camera
be in ‘the form of a heating element 194, as illustrated,
or may spray vapor on the surface to ?x the powder
chamber located so that radiation passing through the
lens will engage an area adjacent one surface of the elec:
The method is well adapted to use in printing or copy 50 tret, a shutter system for the lens adapted to permit pas-'
ing permanent images and employs simple, easily main
sage of light radiation for a predetermined time,’means
for orienting the charge including means for grounding
the surface of an image-forming material adapted to be
placed in juxtapositionover the lens facing surface of the
ferred to.
Thus, it will be seen that we have provided methods 55 electret whereby stray electrostatic ?elds are removed,
and apparatus for electrophotographically taking perma
means adjacent the electret plate for exposing the image
nent images and printing copies embodying principles and,
forming material ‘to an atmosphere of electrostatically
tained and simply constructed apparatus. Copies can be
continuously and rapidly printed with the advantages re
features of the invention hereinbefore set forth.
features of invention are well adapted to use with a
sensitive pigment particles whereby the particles are
coated on the image-forming material with a shape and
camera and avoid the necessity of providing the cumber 60 density varying with the latent image on the surface there- "
some and complicated devices necessary with methods
of in accordance with the radiation received, and means
for ?xing the pigment particles on the surface of the
We have, in the drawings and speci?cations, presented
image-forming material.
a detailed disclosure of the preferred embodiments of our
4. A camera for making an image by an electrophoto
‘invention, but it is to be understood that we do not intend 65 graphic process Which comprises a lightproof camera
to ‘limit the invention to the speci?c forms disclosed, but
chamber, a lens and shutter combination at the front of
and apparatus heretofore used.
intend to cover all modi?cations, changes, and alternative
constructions and methods falling within the scope of the
' the chamber adapted‘to open the lens for radiation to
the back of the chamber in accordance with an image to
be reproduced, an electret plate at the back ‘of the cham-‘
70 her having a surface with an electrostatic charge of 'a
We claim as our invention: 7
1. In combination, a camera means for making an
given polarity, a housing for the camera, means within
image by an electrophotographic process which comprises
the housing for movably supplying a strip of image-form!
a lens‘, a closed camera chamber exposed to light only
principles taught by our invention.
ing material having a photoconductive layer responsive
‘ through the lens, a shutter system for controlling the
opening of ‘the lens and ‘exposing the camera chamber to 75 to radiation through the lens to form an image to ‘be
reproduced, a developing chamber having means for pro
viding an atmosphere of electrostatic responsive pigment
in minute particles which will coat the image-forming
‘conductive insulation layer on the outer surface of the
electret element, means for moving and supporting a ?lm
strip with a shape and density in accordance with the ra
diation received through the lens, and a second ?xing
Within the tubular electret whereby light radiation will
pass through the ?lm and transparent electret to impress
a latent image on the photoconductive insulation layer,
means for applying a powdered pigment material to the
chamber with means to spray a coating of material over
the image-forming strip whereby ‘the visible image is'
?xed on the surface of the image-forming strip.
on the inner surface of the electret element, a light source
' insulation‘ layer on the surface which is attached to the
. layer in accordance with the latent image thereon, a trans
means having an electret plate having opposing parallel 10 fer cylinder positioned to be rotated about an axis parallel
5. In a photoelectric camera combination, _a charging
coextensive surfaces each charged with a permanent elec
with the tube and having an outer surface with an a?inity
trostatic ?eld with opposite surfaces having opposing
for the powdered pigment, a picture material adapted to
be rolled in engagement with the transfer cylinder whereby
polarity, a camera housing supporting said plate and
, the particles are transferred to the surface thereof, and
of the chamber located to expose an image forming strip 15 means for ?xing the particles transferred to said picture
to radiation emitted from an image- externally of the
_ 9. A mechanism for reproducing images in accordance
camera, a shutter system for the lens adapted to open
with claim 8 wherein electrical conductive material is em
the lens for a predetermined length of time, means with
in the housing supplying a stripv of image-forming ma- ‘ bedded in_ the surface of the transfer cylinder to ground
terial of‘a clear plastic with a photoconductive insulating 20 the surface of the electret tube in contact with the trans
forming a lightproof camera chamber, a lens at one end
surface thereon, said image-forming material being drawn
fer cylinder to expedite transfer of the image to the cyl
across the surface of the electret plate, a developing
chamber ?lled with dust particles of pigment susceptible
10. A mechanism for reproducing images electro
photographically comprising a transparent electret ele
ment having ?rst and second surfaces permanently
,charged electrostatically with opposed polarity, a photo
to electrostatic attraction, whereby the pigment particles
are coated on the image-forming strip with a shape and
density dependent upon the radiation received by the
image-forming strip, and a ?xing chamber adjacent the
developing chamber provided with a-coating spray where
by the pigment particles are adhered to the surface of
the image-forming strip to permanize the image.
6.v In an electrophotographic apparatus comprising a
camera housing de?ning a lightproof camera chamber, a
conductive layer on the second surface of the electret ele
ment, a light source located adjacent the ?rst surface
whereby light vrays may be projected through a ?lm
place againstrthe ?rst surface and through the transparent
electret to the photoconductive insulation layer,‘ means
for applying a powdered material attracted by the charge
on the insulated surface whereby a visible image will be
lens member at the front of the chamber for admitting
produced thereon dependent on the intensity of the ra
radiation in accordance with the character of an image,
a shutter assembly for the lens, a light~re?ecting surface 35 diated latent image thereon, a transfer blanket means
having a greater a?inity for the powdered material than
at the back of the camera chamber positioned substan
‘the insulated surface and adapted to remove the pow
tially at an ‘angle of 45° with the axis of the lens whereby
dered material in the charge pattern in which it has
the'light rays will be‘ re?ected vertically upwardly to an
‘formed on the insulated surface, a second electret element
image-receiving position'when the camera is positioned
horizontally, means for ‘movably' supplying a strip of 40 having a permanently charged electrostatic surface with
image-forming material in the‘image-receiving position ' .a polarity opposed to that of said'second surface of the
transparent electret, whereby the second electret may be.‘
across the top of the camera chamber, said material having
‘ pressed against the transfer means with an image-receiving
‘a layer of photoconductive material thereon, an electret
meansv therebetween and the powdered material will at
having a surface located for engagement with the image
forming strip as it is drawn into image-receiving position, 45 tract itself to the image-receiving means in the pattern
of the image, and means for ?xing the material to said
whereby radiation will produce a latent charge image on
image-receiving means.
said photoconductive layer, and means for developing and.
11. A mechanism for rotary printing of images by an
?xing said latent image into a permanent image by sub
electrophotographic process which comprises a hollow
jectingthe strip to an electrostatically attracted dust and
by adhering the dust to the strip after it is accumulated 50 cylindrically-shaped electret having inner and outer sur
faces with a permanent electrostatic charge of opposed
“thereon in the shape and density of the latent image,
polarity, means on the inner surface of the electret cylin
7. In. an electrophotographic apparatus, an electret
member having opposed surfaces permanently charged
with electrostatic ?elds of opposite polarity and having
coatings of electrically conductive material over each of
said surfaces, means for passing an image-forming ma
terial in effective electrical engagement with the ?rst
layer of electrically conductive material and subsequentlyr
in engagement with the second layer of electrically con
ductive material, means for placing a grounded plate in
coextensive juxtaposed relationship with the image-form
‘ der for supporting a ?lm, a light source positioned within
the electret cylinder, a light shield having a narrow light
passing strip extending axially across the cylinder and
limiting the light passage through the ?lm and the elec~
tret to the narrow strip, a coating of photoconductive in
sulation material on the outer surface of the electret,
means for applying a material to the outer surface of the
cylinder which will a?ix itself thereto in the pattern of
the image impressed on it by the light radiation passing
through the electret and ?lm, a transfer roll rotatable
ing material after it has been passed over the conductive
about an axis parallel to the electret cylinder and having
layers, a camera lens system exposing the photoconduc
an outer blanket surface with an a?inity for the material
tive layer on the image-forming material to a radiation
in accordance with an image to be reproduced, and de 65 attached to the surface of the electret cylinder to thereby
remove said material in the pattern of the image, a
veioping and ?xingimeans for permanizing the latent
second rotatable electret having an outer permanently
image on the photoconductive layer by dusting the layer
charged electrostatic surface with a polarity opposite that
with an electrostatically attracted powder and adhering
of the outer surface of the electret cylinder, means for
the powder in its attracted positions in densities and shapes
70 passing a strip of image-receiving material between the
varying with the radiation received by the material.
'8. A mechanism for reproducing images electrophoto
graphically comprising a tubular shaped transparent elec
tret element having inner and outer surfaces permanently
transfer roll and the second electret whereby the image
will ai?x itself to the material, and means for re
ceiving the material from the second electret and opera
tive to ?x the attracted material to the surface for a
charged electrostatically with opposed polarity, a photo 75 permanent print.
a, 028,799
jected into said photoconductive layer when said lens
12. A mechanism for reproducing images electro
photographically (comprising a tubular-shaped transparent
is opened, and a developing chamber into which said strip
material is moved away from said electret and having an
electret element having inner and‘outer surfaces perma
atmosphere of charge-responsive material coating the
nently charged electrostatically with opposed polarity, a
image-forming material non~uniformly with a shape and
density varying with the radiation received from the
photoconductive insulation layer on the outer surface of
the electret element, means for supporting an image
a bearing means on the. inner surface on the electret ele
15. An electrophotographic reproduction apparatus
ment, a light source within the tubular electret whereby -
which includes, an electret,.means passing. a layer'of
light radiation will pass through the image and trans
parent electret to impress a latent image on the photo-j 10 image-forming material having a photoconductive layer
through the permanent electrostatic ?eld adjacent the
conductive insulation layer, means for applying a pow
surface of the electret, means forming a grounded sur
dered pigment material to the insulation layer on the
face in close proximity to the image-forming material,
surface which is attached to the layer in accordance
camera lens means for exposing the photoconductive lay
with the latent image thereon, a transfer cylinder posi
tioned to be rotated about an axis parallel with the tube 15 er of image-forming material to a radiation in an image
to be reproduced to form a latent electrostatic image in
and having an outer surface with an affinity for the pow
the image-forming material, and means for developing
dered pigment, a grounding brush positioned in contact
the image to render it visible.
with the insulation layer after contact with the transfer
cylindena copy material adapted to be rolled in engag
ment’with the transfer cylinder whereby the particles are
16. An electrophotographic reproduction apparatus in
20 cluding an electret, means passing an image-forming ma
transferred to the surface thereof, and means for ?x
ing the particles transferred to said copy material.
13. A mechanism for reproducing images electro
terial having a photoconductive layer attached thereto ‘
through the "permanent electrostatic ?eld adjacent the
surface of an electret, means passing the image-forming
material in electrical contact with a layer of electrically
an electret with the inner and outer surfaces of opposing 25 conductive material on a ?rst surface of said electret, and
subsequently with a second layer of electrically conduc
polarity, means for attaching a thin plastic material with
tive material on another surface of said electret, means
a photoconductive insulating surface thereon to the outer
pho'tographically comprising a rotating cylinder forming
placing ‘a coextensive ground adjacent the image-forming
peripheral surface of the cylinder wherein an image-bear
material, a camera lens system for exposing the image
ing ?lm may be held between the plastic material and
cylinder, a light source exteriorly of the cylinder adapted 30 ‘forming material to a radiation in accordance with an
image to be reproduced to formulate an electrostatic
to apply light radiation to the photoconductive surf-ace of
image on the photoconductive layer, and means for de
the thin plastic material, a dust chamber for applying a
veloping and ?xing the image on the image-forming ma- ' '
.pigment dust to the outer surface of the plastic material
whereby the latent image is rendered visible, and a second
electret cylinder having an outer surface permanently 35
electrostaticall-y charged and being of a polarity opposing
ders, said paper receiving'the image in its visible form
from the layer of thin plastic material as attracted by 40
the surface of the second electret.
14. In combination in a camera for making an image
‘by electrophotography comprising a closed light-proof
‘camera chamber, a lens located at one end of the cham 45
ber, a shutter device to be opened to expose the interior
of the closed chamber through the lens to an image to be
photographed, an electret in said camera having a flat sur
face facing said lens and possessing a permanently pre
charged electric ?eldof a given polarity, ?lm advancing 50
and guide means movably positioning strip form image
forming material having a layer of photoconductive ma
terial in adjacent coextensive relationship across said flat
surface of said electret, whereby radiation may be pro
References Cited in the ?le of ‘this patent
the polarity of the outer surface of the ?rst electret cylin
der, means for passing a copy paper between said cylin
2,221,776 I
Carlson _____________ __ Nov. 16, 1940
,Carlson ..__ ____________ __ Oct. 6,
Oughton et a1 __________ .._ Feb. 27,
Carlson ______________ _.. May 8,
Butter?eld __________ __ Nov. 2,
' Marvin _____________ .._ Nov. 23, 1954
2,732,775 -
Young et al. _________ __ Jan. 31, 1956
Mayo et al. ___________ __ Feb. 19, 1957
Bixby et al. __________ __ Apr. 22, 1958
vI-Iayford _____________ __ July 15, 1958
'Review of Modern Physics, \vol. 20, No. 3, July 1948, _
page 470.
Electrical Engineering, October 1953, pages 869-872. V‘ I
Radio Electronics, January 1950, pages 8-82.
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