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Патент USA US3083632

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_' April 2, 1963
Filed June' 12,_1959
2 Shee’cs--Sheetv 1
Daniel Frank/[h 'Kel/er.
M'l/l'am R. Bea/r, ‘Jr: '
United States Patent O??ce
ous basis.
Other objects and features of the present invention
will be apparent to those skilled in the art from the fol
lowing description of the attached sheets of drawings
which illustrate a preferred embodiment of the invention.
In the drawings:
The present invention relates to improvements in xero
plates or for reproducing copies in a substantially con
FIGURE 1 is a view in elevation, and partly in cross
tinuous operation.
Photographic xerography involves the formation of an
with a ?nely divided powder which adheres to the elec
section, of a camera mechanism embodying the prin
ciples of the present invention;
FIGURE 2 is a view in perspective of the vacuum
b-acked carrier employed in the apparatus of FIGURE 1;
electrostatic latent image on a layer of photo-conductive
insulating material and the development of the image
Patented Apr. 2, 1963
A further object of the invention is to provide an im
proved method for xerographic photography on a continu
Daniel Franklin Keller, Kenilwerth, and ‘it'v’illiam R. Beck,
.Ir., Ncrridge, Kih, assignors to Robertson Photo
Mechanix, ind, Chicago, Ill., a corporation of Illinois
Fiied June 12, 1959, Scr. No. $19,351
1 Claim. ((31. 95-437)
graphic methods and apparatus for producing printing
FIGURE 3 is a fragmentary cross-sectional view
taken substantially along the line III—III of FIGURE 1;
trically charged areas of the plate. The plate is sensi
tized by applying an electrostatic charge to the surface
of the photo-conductive coating. The sensitized plate is
FIGURE 4 is a wiring diagram for the circuits em
ployed in the structure of FIGURE 1.
As shown in the drawings:
then exposed to the light image which it is desired to re
In FIGURE 1, reference numeral 10 indicates gener
produce. Impin-gement of light on the photo-conductive
ally a light-tight chamber which includes the transporting
coating causes electric charges to leak away or to be re
mechanism, vexposure mechanism and developing mecha~
nism involved in the xerographic process.
A vertically movable platform 11 disposed within the
duced in quantity in proportion to the ‘amount of light
falling on the particular area, thus leaving an electrostatic
latent image. The image is developed by dusting the plate
with a ?nely divided powder which adheres only to the
electrically charged areas in proportion to the amount of
charge remaining on the plate after exposure to light.
The photo-sensitive plate consists of a photo-conductive
25 chamber Ill carries a plurality of sheets 12 of xerographic
plates, normally consisting of paper sheets having a coat
ing of a suitable photo-conductive material such as vitre~
ous selenium. The platform 11 is adjusted vertically by
the provision of a pair of opposed pivot arms 15 and 13
secured to their respective shafts l4- and 16 and connected
by means of a tie arm 17. A manually operable lever
18 secured to the shaft 14 permits vertical adjustment of
the platform 11 as the individual sheets ‘12 are used in the
coating of vitreous selenium or the like on a backing of a
material having a speci?c electrical resistance below the
equivalent resistance of the photo-conductive layer. Thus,
materials such as paper, glass, and plastics have been
employed for backing materials.
The most common means for charging the photo-con
The mechanism employed for transporting the individ
ductive layer to render it light sensitive consists in intro
ual sheets 12 through the assembly is best illustrated in
FIGURES 1 and 2 of the drawings. As best seen in
ducing the photo-conductive layer into an area of ions
formed by corona discharge. ~ The discharge is normally
FIGURE 2, the vacuumebacked carrier, generally illus
produced by applying a potential of several thousand volts
trated at numeral 19 in FIGURE 1, consists of a rec
on series of fine wires, so that the resulting electric ?eld 40 tangular frame 21 carrying a plurality of rollers 22, the
strength at the surface of the wires causes air molecules
rollers 22 being arranged to ride on opposed tracks 23
to be ionized.
extending horizontally along the walls de?ning the sides
The developing powder employed in one exemplary
of the chamber 10.
form may consist of two components, a ?nely ground
A cover 24 is hinged to the frame 22 by means of a
pigmented resinous powder known as a toner, and a rela
piano hinge 26 and is provided with a handle 27 to facili
tively large granular material having particle diameters
tate raising the cover 24 into the raised position illustrated
of about 1A; to 1/z millimeter, known as a carrier. The
in dashed lines in FIGURE 2. A vacuum manifold 28
carrier serves to add mass to the developer used on the
is disposed at the rear of the cover 24 to apply a source
exposed xerographic plate and also charges the powder
of reduced pressure from a line 29 to a series of slots
31 formed in the face of the cover 24, as best seen in
particles to the correct polarity by a phenomenon known
as triboelectri?cation.
These electrical charges are gen
The frame 21 is secured to a chain 32 driven by a
erated by the intimate contact between the dissimilar mate
rials when the developer components are simply mixed
sprocket 33 lwhich, in turn, is driven by a reversible
together. As a toner-laden carrier particle passes over an
motor 34.
When a source of reduced pressure is applied to the
electrical discontinuity in the surface of the plate, the
vertical component of the fringing ?eld exerts a su?icient
vacuum manifold 28 through the conduit 29, the vacuum
ly large force on the toner particles to overcome the car
carrier 19 picks up a sheet 12 of the stock of sheets on the
rier-to-toner bond and the toner particles then attach
themselves to the plate in the image area.
The present invention is directed primarily to an im
platform 11, and the movement of the carrier 19 takes
the sheet, with its sensitized surface down, from a load
ing station indicated generally at A into a charging sta~
proved method and apparatus for Xerographic photog
tion or area shown at B, for example, into an ionized ?eld
raphy in which the sensitized xerographic plate is trans
ported to an exposure zone, exposed, and developed as
a continuous operation.
An object of the present invention is to provide an
improved apparatus for the manufacture of xerographic
exposures suitable for use as printing media.
Another object of the invention is to provide an appa
ratus for xerographic photography including a vacuum
backed carrier which transports the Xerographic plate
from a supply ‘station through the charging, exposure, and
developing stations in a continuous fashion.
produced by a corona discharge head 36. The latter in
cludes a plurality of wires charged to a potential on the
order of 4,000 to 10,000 volts, causing ionization of the
air molecules in the immediate vicinity of the 'wires. As
the sensitized sheet passes through the electrostatic ?eld
‘ adjacent the corona discharge, the sheet receives a uni
form electrostatic charge enabling it to receive an image
from a suitable light source at an image receiving station
shown generally at C.
After passing over the head 36, the carrier 19 trans
ports the sheet to the image receiving station C which may
include a photographic lens system of a camera generally
indicated at numeral 37 of the drawings. The adjustable
portions of the photographic system of the camera 37
may be preadjusted in connection with a vertically mov
able ground glass screen 38. The screen 38 is pro-‘posi
tioned in the plane of the image member 12 whereupon an
adjustable stop means may be preset to provide a posi
tioning stop for the movable carriage 19 in the image
station C. After the carrier 19 is positioned in the
three~position switch 66 is then moved to the “focus” posi
tion and thereby applies line voltage across a shutter
mechanism 67 to open the shutter and permit focusing
of the photographic system on the ground glass plate
assembly 368. After this adjustment, the ground glass plate
38 is raised, thereby closing switch 41. Next, the switch
66 is moved to the “on” position. Since the vacuum‘
backed carrier 19 is abutting the limit switch 55 at this
time, line voltage is applied across a relay 67 having 3
image receiving area C, it also strikes a contact arm 38 10 sets of contacts, 67a, a holding contact, 671), a contact lo
cated in the timer clutch mechanism, and 670, a contact
of a switch assembly 39 causing the carrier 19 to be
located in the energizing circuit for the corona device 36.
stopped, by deenergization of the motor 34.
When the ground glass screen assembly is lowered into
the position desired for centering the image and other
The vacuum applied to the manifold 28 by operation
of the vacuum pump 64 conditions the plate to‘ retain an
adjustment, a switch 41 is deactivated by an arm 42 15 image {bearing member when platform 11 is elevated to
lift a sheet 12 onto the face of the carrier 19. When this
thereby deenergizing the motor 34. In the normal, re
occurs, a pressure sensitive switch 68 in the vacuum line
traeted position of the ground glass screen assembly, the
29 is closed. Then, operation of the “start” button 58
arm 42 closes the switch 41 to make the conveyor system
serves to energize a relay 69, closing its three contacts 69a,
The operation of the switch 39 also serves to energize 20 a holding contact, 6%, a contact which serves to energize
the corona device 36, and 690, a normally closed contact
a timer 43 which is preset to determine the exposure
which opens the reversing circuit of the drive motor 34.
time for the photographic system. Any suitable aerial
The closing of contact 6% also serves to apply the line
image is projected by the camera 37 onto the image mem
voltage across the drive motor 34 so that the conveyor
ber 12. At the conclusion of the required exposure in
terval, the timer reenergizes the motor 34 so that the now 25 mechanism is rendered operative in the forward position.
exposed xerographic plate bearing a latent electrostatic
image is passed to a developing station indicated generally
at D where the latent electrostatic image produced during
the photographic exposure is developed, for example,
As the conveyor mechanism moves the vacuum car
rier 19 away from the supply station, the limit switch 55
is opened, but energization of the relay 69 is maintained
through the holding contact 69a.
The vacuum carrier i9, carrying the sheet 12 then en
with a mixture of toner powder and carrier particles.
ters the image receiving station, and eventually the car
The ‘applicator or developing station D may include a
rier 19 closes the switch 38, thereby energizing a clutch
trough 44 containing a supply of the powdered xerographic
71 associated with the timer motor 43. Closing of the
developer mixture, and a rotary magnetic brush assembly
switch 38 also serves to energize a relay 72 having a pair’
46 arranged to pick up the developer particles and apply
of contacts 72a and 72b. The former is a normally
them to the surface of the exposed xerogra-phic plate.
closed contact in the energizing line for the corona dis
The brush assembly 46 is rotated in a counterclockwise
charge device 36, and opening of the contact 72a thereby
direction as viewed in FIGURE 1. A substantially uni
deenergizes the corona discharge device. The second‘
form deposit of the developer particles is thus applied to
contact, 72b, serves to open the shutter 67 of the photo
the sheet and excess particles for the most part fall back
into the trough 44. The brush assembly 46 is rotated by
graphic mechanism.
At a predetermined time interval after the timer clutch
means of a motor 47 driving a chain 48 which in turn
71 engages, rotation of the timer shaft serves to open two
rotates a sprocket 49‘.
The exposed xerographic plate, with the developed
normally closed contacts 73 and 74. The opening of
image then moves past a safety switch 51 and eventually
strikes an arm 52 of a limit switch assembly 53.
the contact 74 thereby serves to close the shutter 67.
The 45 Opening of the contact 73 serves to deenergize the relay
67 thereby releasing the time-r clutch 7'1 and deenergizing
operation of the switch 53 deenergizes the motor 34 and
stops the conveyor system.
The vacuum carrier plate 19 may then be removed
from the conveyor assembly and opened to remove the
‘zation of the relay 72 thereby reapplies the line voltage
the resinous particles making up the exposed areas.
plies the mixture of toner particles and carrier particles’
relay 72. The closing of the contact 72a upon deenergi
across the drive motor 34 and renders the motor operative
exposed sheet from the face of the cover 24. The ex 50 to resume operation of the conveyor mechanism.
posed sheet can then be ?xed in any suitable manner, for
The exposed xerographi-c plate then moves to a develop
example, a heat treatment which serves to set or solidify
ing station where the brush 46, driven by motor 47 ap
The cover '24 of the vacuum car-rier ‘19 is then lowered
to the exposed face of the xerographic plate.
and a ‘reversing button 54 is operated to reverse the direc 55
As the vacuum carrier 19 moves toward the end of the
tion of rotation ‘of the motor 34, and transport the carrier
conveyor system the carrier 19 engages the limit switch
back to the supply station A. Upon reaching the supply
52 thereby deenergizing the relay 69‘. Contact 6%
thereupon opens, deenergizing the drive motor '34 and
station, the vacuum carrier '19 contacts one of a pair of
limit switches 55, 56 and thereby deenergizes the motor
stopping the conveyor system.
34. The cycle is thus completed, and re-initiated by the 60 The carrier 19 is then opened to remove the exposed
operation of “forward” button 58. The sequence of
and developed xerographic plate. Upon movement of
operations, and the control circuits therefore, can best be
the cover 24 about hinge 26, the safety switch 51 is
described in conjunction with the schematic wiring dia
opened. After removal of the developed plate, and clos
gram constituting FIGURE 4 of the drawings.
ing of the cover 24, switch 561 closes. Then, pressing the
The entire assembly is energized by closing a line 65 reversing switch 54 causes energization of a relay 76 hav
switch 61 connecting the assembly to a suitable source
ing three contacts 76a, a vholding contact, 76b, which
of voltage. Next, a switch 62 is closed to energize lights
energizes the reversing circuit for the motor 34 and 760
63 which illuminate the copyboard on which the material
which opens to deenergize the magnetic brush driving
to be photographed is located. Next, a switch 63 is closed
motor 47 and the vacuum pump 64.
to energize the magnetic brush rotating motor 47 and to
The vacuum carrier 19 thereupon returns to the supply
energize a vacuum pump 64 to which the vacuum line 29
station and at the limit of its travel strikes the switch 56
thereupon deenergizing the relay 76 and putting the en
is connected.
To adjust the photographic system prior to making
tire system in readiness for another sequence of operation.
prints, the ground glass screen 38 is lowered to the image
It will thus be seen that the apparatus of the present
plane of the photographic system, thereby opening the
invention provides a complete and automatic assembly
switch 41, deenergizing the remainder of the circuit. A
for providing xerographic exposures and developing on
a continuous basis.
It will also be evident that various modi?cations can
the plane of said copy sheet when said holder is at
said stop position,
thereby to ?orrn an electrostatic image on the photocon
be made to the described embodiment without departing
ductive material,
from the scope of the present invention.
and a xerographic brush extending transversely of said
We claim as our invention:
A xerographic machine for reproducing images directly
on sheet-form copy media having a photoconductive coat
ing thereon which comprises,
opposed tracks disposed horizontally and extending 10
a vacuum back sheet-form holder having
a carriage supported for movement on said tracks,
a platform subjacent one end of said tracks for carrying
a supply of copy sheets,
tracks having
means for extending tufts of developer material
in the form of a brush for contact with the copy
sheet as the said holder is moved away from said
stop position,
thereby to develop the image.
References Cited in the ?le of this patent
pick up and carry one copy sheet at a time from
said platform,
a ‘corona charging unit for forming an electrostatic 20 2,630,743
charging ?eld at a location adjacent said platform
and through which the copy sheet is moved by said
a motor drivingly connected to said carriage to move
said carriage on said tracks,
25 2,790,082
pre-settable stop means for stopping said carriage and
said motor at a stop position after said holder has
said platform and said holder being relatively
vertically adjustable whereby said holder may
moved the copy sheet through said charging ?eld,
a camera having a lens system for focusing an image
to be reproduced onto a focal plane coincident with 30
Carlson _______________ __ Oct. 6, 1942
O’Kane _____________ __ Mar. 10, 1953
Skinner ______________ __ May 4, 1954
Ransburg _____________ __ July 27, 1954
Carlson _____________ _.. Sept. 28, 1954
Walkup ______________ __ Jan. 15, 1957
Gundlach ____________ .._ Apr. 23, 1957
Whitham _____________ __ Dec. 1, 1959'
Francis _____________ _._ Nov. 29, 1960‘
Ernst ________________ __ May 23,
Simjian ______________ __ Mar. 27,
‘Carlson ______________ __ Nov. 19,
Great Britain __________ __ Feb. 9,
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