Note: Descriptions are shown in the official language in which they were submitted.
~ 3 ~
The invention relates to the making o~ offset printing
plates and more particularly to a transfer attachment for
a camera for transferring an image from an electrophotograp~ic
film to a plate material.
Offset plates are made photographically by complex
methods requiring the use of silver halide film, photoresists~
and the processing o~ the images to achieve their incorporation
onto plates that can be used on printing presses. In recent
years electrostatic techniques have also been used to make
such plates, but their quality is so inferior to the quality
of photographically made plates that this type of technique
is utilized rarely.
The invention herein revolves around a type of
electrophotographic film that is capable of being imaged with
quality and grey scale as good as, if not bett~er than, that
achieved by photographic techniques and with resolution that
is better than that achieved by photographic techni~ues
The film includes an inorganic coating of microcrystalline
material that is bonded onto a polyester substrate with an
intervening ohmic layer to aid in charging the film. The
film material comprises a coating of radio frequency sputtered
cadmium sulfide that is from about 2,000 Angstroms to abou-t -~
2 microns thick disposed upon a layer of about 300 to 500
Angstroms thick of indium tin oxide which in turn is disposed
on a sheet of stable polyester plastic about 5 microns thick.
one such film material is described in U.S. Patent No. 4,025,339
issued May 24, 1977.
~.
The film may be exposed at a high speed and transferred
immediat~ly to a carrier such as paper, aluminum, plastic
and the li~e which enables the entire process to be carried
out inside of an attachment or cartridge which takes the
place of the usual silver halide photographic film cartridge
that is currently used with graphic art cameras. Besides the
elimination of the silver halide film this eliminates
considerable processing since the carrier or plate medium with
the transfer image may be fixed and directly immersed in a
suitable bath to render the toned and untoned parts of the
; image ink receptive and ink repellant, respectively and then
utilized directly as a printing plate in a press.
The disadvantages of the previous proposals may be
overcome by replacing a graphic art silver halide film cartridge
with an attachment having an endless web including at least
a portion of electrophotographic film onto which an image may
be formed. The film portion is rotated to and charged by a
corona source, rotated to an exposure station where an image is
formed, then rotated to a toner station where toner is applied
to the image and finally to a transfer station where the image
is transferred from the film portion onto a second medium,
such as a plate material for use in an offset ~rinting press.
This aliminates the silver halide film as well as the consider-
able processing necessary for silver halide film.
~3~5'7~
The preferred embodiments of this inven~ion will now
be described, by way of example, with reference to the
drawings accompanying this specification in which:
Figure 1 is a perspective partially sectional view of
one embodiment of the transfer attachment of the invention;
Figure 2 is a diagram of the attachment of Figure 1
showing the basic parts and construction thereof;
Figure 3 is a timing diagram illustrative of the
operation of the attachment;
Figure 4 is a perspective diagram of a second embodiment
of the attachment;
Figure 5 is a diagram of the embodiment of Figure 4
showing a second type of transfer mechanism;
Figure 6 is an enlarged diagram of the toner station
of Figure 4;
Figure 7 is a diagram of another embodiment of the
toner station to be used with the attachment; and
Figure 8 is a side sectional view of a toning manifold
which may be used with the attachment.
Offset printing plates are made by a technique which
requires that the image to be incorporated into the plate
be photographed. The cameras which are used are specialized
for the purpose and commence the process by exposing silver
halide film contained in cartridges that are secured to
the back of the camera at the image plane thereof. The
attachment o~ the invention is intended to replace the silver
halide film cartridges and may be utilized with graphic art
cameras and other cameras only requiring that the camera
~3;~5'7~
system contain the conventional lenses, shutters, and
focusing equipment to expose the film portion by contact,
projection or reflection of an object.
Figures 1 and 2 illustrate one embodiment of the
attachment 10 of the invention. The camera system is only
shown diagrammatically by a lens 12 but would include the
elements previously mentioned. The attachment 10 has been
shown totally exposed; however, of course, the attachment IO
and the lens 12 would be married together such that no light
would enter the system except as desired through the lens 12.
In this respect a cover would be fastened over the attachment
10 which is not illustrated.
The attachment 10 includes a sequence o~ stations
incluaing a charging station 14, an exposure station 16, a
toning station 18 and a transfer station 20 which may be
~ollowed by an optional cleaning station 22. An endless
web 24 is rotated through the stations and the web includes
a portion of electrophotographic film upon which the image
may be projected and transferred from. The web 24 need only
contain a portion of electrophotographic ~ilm large enough
to cover the area to be imaged in the exposure station 16;
however, the web 24 may be made entirely from the electro-
photographic fi]m. One electrophoto~raphic film which may be
utilized in the invenkion as previously mentioned is described
in United States Patent ~o. 4,025,339 issued May 24, 1977.
In operation a starting point on the web 24 is chosen,
prior to the ilm portion to be acted upon, such as a point
on the periphery of the web 24 which may be a piece of
--4--
~ 3~S ~
metallic material or strip 26. The strip 26 may then be
optically or magnetically sensed as the web 24 passes to the
various stations to control the operations and timing o~ the
attachment 10. There may be a second metallic strip 27 on
the opposite periphery of the web 24 which may be sensed by
sensors on the opposite side of the attachment. The timing
of the device may also be accomplished by conventional timing
mechanisms such as a timing belt or counter withou~ the use
of the sensors and strips.
The overall operation of the attachment 10 will be gi~en
prior to the details of the various stations to set forth
the environment of the stations. The attachment 10 is
operated by starting the web 24 rotating through the various
stations When the ~ilm portion to be exposed reaches the
charging station 14 it will be charged by a corona source
either as it moves by the corona source or by stopping the
web and moving the corona relative to the ~ilm portion.
Once the film portion is charged the web is rotated until the
film portion is located in the exposure station 16 where it
is stopped and exposed by the camera system through the lens
12. The film portion is then rotated through the toning
station 18 where toner is applied to the image whic~ has been
projected onto the film portion. The web 24 continues to
rotate until it reaches the transfer station 20 where the
toned image is transferred from the film portion onto a plate
or other transfer medium. Once the image has been transferred,
the web 24 will continue its rotation through the cleaning
station 22 where any remaining toner or other material will
-5-
~.3~
be cleaned from both sides o~ the web 24 and the web is
then rotated completely around to the start position ready
for the next imaging and transfer operation. The cleaning
station 22 is optional, because the operation of the
transfer attachment 10 to a fully receptive trans~er medium
under the proper conditions would remove all the toner
~rom the film portion leaving the film portion ready to be
recycled for the next imaging operation without the
intervening cleaning step.
The components of the various stations and the
detailed operations thereof will now be set forth. The
charging s~itation 14 includes a corona voltage source 28
t~hich contains a corona wire or wires 30. The corona voltage
sou~ce 28 may be fixed to charge the film portion as it passes
over the corona source and wire 30 or it may oscillate to
provide an even distribution of charge on the film portion.
The film portion as utilized hereinafter is that portion of
the we~ 24 which is chosen to be exposed in the exposure
station 16. The film portion may also be stopped and the
corona source ~8 may be moved across the film portion to
provide the even distribution of charge on-the film portion.
The corona source 28 will preferably be operatea at a voltage
of approximately 6,000 volts.
Once the film portion is charged to 8 x 10 coulombs/cm
or 30 volts e~uivalent the charged film portion is moved into
the exposure station 16. The exposure station 16 includes an
exposure platen 32 which is disposed above the web 24 with
a lower smooth planar surface 34 disposed below -the
--6--
~13~
untensioned plane of the web 24 between the rollers 36 and
38. The surface may be beveled at each end to facilitate
the passage of the web thereover and the surface will be
located in the image plane of the camera system and lens 12.
S Thus, the web 24 will be drawn tightly and smoothly across
; the bottom surface 34 so that a smooth unwrinkled surface
will be presented to the camera system and lens 12. To
further facilitate the passage of the web 24 past the
platen 32, the platen 32 is preferably provided with a series
of passageways (not shown) disposed across and opening to the
bottom surface 34 which are connected to a source ~f positive
fluid pressure (not shown). The pressure source is energized
when the belt 24 is moving, but is deenergiæed when the
belt is stopped in the exposure station 16 so that the film
24 will be drawn against the smooth platen surface 34.
Once the film portion has been exposed it is rotated
-over the ohmic roller 3~ and across -the airection rolls 40
and 42 in the toning station 18. The web 24 is tensioned
between the direction rolls 40 and 42 to form a smooth planar
reach with a gap between the film portion and a toning platen
44. The toner in liquid or dry form is applied in the gap.
Preferably, the toner in liquid form is supplied through at
least one of a pair of manifolds 46 and 48 (Fig. 1).
Pre~erably the manifold 46 is used in conjunction with the
manifold 48 to form a smooth nonturbulent flow of toner in
the ~ap formed between the toning platen 44 and the film
portion. A toning bias, preferably, is electrically applie
between the toning platen 44 and the web 24 to assi-st in the
--7--
J'\ ,:`
..
~3~7~
: toner particles adhering to an ima~e on the film por-tion.
The toning platen 44 has an upper generally planar
surface 50 between the rolls 40 and 42 to maintain the gap
between the film portion and the toning platen. An upper
shoe 51 may be utilized which has a bottom planar surface 52
disposed parallel to the surface 50. The surface 52 keeps
- the film portion planar between -the rolls 40 and 42 to
precisely maintain the gap. The toning bias may be in a
range of negative 5-25 volts, preferably about 11 volts.
The gap may be in a range of 5 to 40 mils, preferably about
12 mils. The upper surface 50 of the toning platen
44 is smoothly polished so that the toning particles and
fluid will flow smoothly over the surface thereof and not
become adhered to any particular portion thereof.
Any excess toner is removed from the film portion
by an extraction roller 53 as the film portion passes by
the extraction roller. The extraction roller 53 is spaced
from the web 24 which space may be less than 6 mils,
preferably about 4 mils, and it is electrically biased to
withdraw the toner particles which are not firmly biased to
withdraw the toner particles which are not firmly adhered
to the imaged portion of the film. The bias may be in a
range of negative 20-250 volts, preferably about 135 volts.
The toner particles and liquid are removed from the
extraction roller 53 by a squeegee 54. The toner which is
not utilized and the fresh toner are cap-tured in a tray
or reservoir 56 which is located benea-th the other components
of the toning station 18.
To assis-t in -the extraction of the excess toner
particles from the Eilm portion a spray bar 58 is located
~ - 8 -
above the extraction roller 53 and will spray a film oE
toner into the gap between the web 24 and the ex~rac-tion
roller 53 to provide a medium for the toner particles and
the electric field between the extraction roller and the
film to allow the excess toner particles to be removed.
The web and film portion continue rotating from the
toner station 18 over a guide or direction roller 60 to the
transfer station 20. The.trans:~er station is pre:~erably
loaded with a trans~er or plate medium 62 prior to the
start o~ the operation of the attachment. The medium 62 is
loaded into a first chute 64 which directs the medium past
a tangent point oE the web 24 but spaced thereErom. The
web 24 passes over another roller 66 in the transfer station
20 which locates the web and the film portion as it passes
through the transfer station. A freely rotatable transfer -
roller 68 is disposed for pivotal movement away from and in
close proximity to the web 24 such as on a pivot arm 70,
The transfer medium 62 such as a piece oE paper extends be-
tween the two rollers 66 and 68, but is not in contact with
the web 24. Preferably, the medium 62 will extend into a
discharge chute 72 to precisely locate the medium 62. When
the fron-t edge of the imaged portion arrives in the transfer
station 20, the trans~er roller 68 is pivoted against the
medium 62 to bring it into close proximity with the web 24
to transfer the image to the medium 62 which will rotate
with the rotating belt 24 between the rollers 66 and 68. A
_ g _
t~
.,. , . , " . ~
~ ~3;:~5~
`~ -trallsEeL bias mc~y be applie~ ~t-/een Lhe ro~l~r 6~ alld ~he
web 2~1 and m~ be in -the rancJe of nec~ative 250-1200 volts.
The trallsfer bias should be just sufficient -to fully
-transEer all~ toned imacJe and will preEerably be about
ne;~ative 500 volts. The roller G8 may brincJ the m.diuln 62
directly ac~ainst the fllm portion or may leave a slicJht c~ap
to avoid mechanical smearinCJ o~ tlle im~ge i~ th~ me~ium 62
will not absorb the fluid surro~nc~in~ the ton~r particl~s
on the f iln~ portion. The gap may be in the ran~e of 0-4
microns.
The web 24 then moves on into the cleaning station 22
- where it passes around another roller 7~ and past a foam
cleaning brush 7~ which dislodc~es àny firmly a-ttachèd toner
particles or other Material wllicll have not been removed by
the -transfer operation. The web 24 then passes pas-t a
cleanincJ spray bar 78 which sprays a cleaning ~luid against
the film which is squee~eed by an air brush or knife 80 which
provides a smooth flow of air across the widtll of the film
and may contain a fluid baEfle (not shown). The nozzle
20 ot the air brush 80 is coated with a non-abrasive material;
however, the web and film portion thereof preferably will not
touch the air brush due to the flow oE -tlle air from the
nozzle. The cleaning solution and excess toner particles are
cau~ht in a reservoir 82 loca-ted at -the bottom of the cleaning
station 22. The back or inside of thè web 2'~ is cleaned by a
squeegee 8~ as it passes the adjustablc ohmic ~uide roller 36.
Tlle ohmic roller 36 has an acljus-tment at each end 86, one of
W]liCll is sllown, to steer the web aroull(l tlle se~ts of rollcrs
~ ' -- 1 0
~1 13~5~7~
in the attachment 10 without excessive lateral movement
thereof. The web 24 then continues through the other sta-tions
without their being energized and returns to the initial or
stop position ready for another cycle. As previously mentioned
with the proper biasing, toning and transfer conditions
cleaning station 22 may be eliminated.
Referring now to Figure 3, a timing diagram ~or the
attachment 10 is illustrated; however, it should be noted
that the time factor between each of the times To through
Tlo is not drawn to scale and these will vary as determined
by a particular operation, size of components, etc. The
operation will be explained with the timing diagram utilizing
the sensors Al through A6 which sense the metallic strips
26, 27 along the peripheries of the web 24, ~
At time To the start mechanism is energized which will ~;
activate a drive motor 88 starting the web rotati~g, energizing
the ~ressure valve in the exposure platen 32, rotating the
extractor roll 53 and applying the bias to the extractor ro]l~
At time T2, upon sensing the strip 26 by the sensor Al, the
corona voltage source 28 will be energized and the charge will
~e applied to the film portion until time T3 when the strip 26
is sensed by the sensor A2. At time T3 the drive mo-tor will
stop, the corona voltage source will deenergize, the pressure
valve and the exposure platen 32 will deenergize, drawing the
film against the platen surface 34. The ex-tractor roll 53
will also stop rotating as it is geared to the drive motor
88; however, it could be kept rotating by a separate drive ;
if desired. The ~ilm portion is then exposed by the camera
- 11 - ' ,
. .
~13qS~
throuyh the lens 12 by openiny a shutter within the camera
to project a light image onto the film.
At time T~, prior to the end of the exposure and the
restart of the rotation of the web 24, the toner pump
; 5 (not shown) will be operated to flow toner through the
manifolds ~6 and 48 and the extractor spray will be operated
to fill the gap between the ex-traction roll 53 and the web
24 with toner so that the extraction roll will be operating
properly. At time T5 when the film portion has been properly
exposed, an elapsed time of 1-10 seconds,, the drive motor 88,
the pressure valve in the platen 32, the toner bias on the
platen 44 and the extractor drive are actuated. The film
portion then moves through the toner station 18 and is sensed
by the sensor A3 at time T6 indicating that the fi-m portion
has passed through the toning station. This will deactuate -
the toner pump and toner bias and the film portion will be
transported to the transfer station 20 during the time
period from T6 to time T7.
At time T7 when the strip 26 is sensed by the sensor
A4 the drive motor 88 will increase its speed for the
transfer operation as it has been found -that the toning
operation is more successful at a lower speed than the transfer
operation, The web 2~ ma~ move through the toning station at
approximately S inches/second and may be transferred at a
speed of approximately 8 inches/second. As the front edge of
the film portion moves into the transfer station 20 the strip
27 is sensed by the sensor A5 at time ~8 which actuates the
bias on the transfer roller 68 at the same time it is actuated
- 12 -
.~
` ~133~i7:~L
to move against the medium 62 and press it into close
proximity with the belt 24 to pass the medium 62 intimately
against the film portion of the web 24 as it passes between
the two rollers 66 and 68. The first time that ~he strip 26
is sensed by the sensor A6 at time Tg it ener~izes the
components of the cleaning station 22 and the web 24 then
rotates through each of the stations to clean off any residual
material from the belt. When the sensor A6 senses the strip
26 a second time at time Tlo all the systems and stations are
deactivated and the web 24 is stopped ready for the next
imaging and transfer operation.
Referring now to Figures 4 and 5, a second embodiment
o~ the attachment 10' is illustrated. In this embodiment,
the charging station 14 and the exposure station 16 remain
the same as described previously; however, the cleaning
station 22 has been eliminated and a different toning station
18' and transfer station 20' are utilized. The basic operation,
with the exception of the cleaning operation, remains the
same as described previously. The various rollers of
Figures 1 and 2 have been replaced by two main support rollers
90 and 92, one or both of which are engaged with the motor to
frictionally rotate the belt 24 as before. A third adjustable
steering roller 94 is inserted in one end of the belt 24 to
assure proper alignment of the belt in a like manner as the
adjustable roller 36. The roller 94 is connected to a swivel
bar 96 which is secured to adjustably pivot around a center
point 98 to properly adjust the tracking of the web 24. ~
The center point 98 could of course be replaced by two or ~ -
- 13 -
~ "
more adjustable points on the outer ends of the swivel bar
96 as described before.
The film portion on the web 24 is again charged and
exposed as before; however, the toner is applied b~ a
rotating toner ~eed roll 100 which adhesi~ely picks up the
toner from the toner tray or reservoir 56 and applies the
toner in a smooth uniform manner across the width of the
film portion o~ the web 24. As previously mentioned, the
toning platen 44 and the upper shoe 51 may be provided to
maintain the optimum gap between the web 24 and the toning
platen 44. The toner stations 18 and 18' are, of course,
interchangeable as desired.
Once the film portion has been toned it continues around
the roller 94 to the transfer station 20'. In this embodiment ``
tne film portion would be rotated until the front edge of
the portion is located toward the end of the transfer station
20' The web 24 is then stopped and the medium 62 is then
brought into close proximity with the web 24 for the transfer
operation. The film portion of the web 24 is brought into
close proximity with the medium 62 by a reciprocating transfer
roller 102 which is disposed parallel to and below the web 24.
Referring to the timing diagram of Figure 3, the sensors :
A4 and A5 would be replaced b~ a single sensor and the times
T7 and T8 would coincide and the drive motor 88 would stop,
stopping the ro-tation of the web and the transfer bias would
be applied to the medium 62, not to the roller 102. The
roller 102 would be activated and move the roller into the
position 104 illustrated in phantom to reciproca-te the roll.er
- 1133S~
102 across the film portion, sequentially bringing -the ilm
portion of the web 24 into close pro~imity or contact with
the medium or plate 62 across the entire length thereof.
The roller 102 would then be returned to its initial position
away from the web 24.
- One convenient method of locating the medium 62 parallel
to the upper reach of the web 24 is a vacuum platen 106.
The vacuum platen 106 has a first open or load position 108
which exposes a bottom planar surface 110 having the vacuum
or other negative fluid passageways (not shown),opening :'
thereto, The paper or plate material 62 such as aluminum is
; placed onto the platen 106 in the load position 108 and then
the vacuum source (not shown) is operated to clamp the plate
medium 62 to the platen 106 which is then pivoted or otherwise
movea to the transfer or receiving position 112. The platen
106 may contain other means to affix the medium 62 to the
surface 110 and may be conveniently moved between the open ~,
position 108 and the receiving position 112 by pivoting it
around a pivot 11~. The transfer bias would be applied to the
platen 106 and when the transfer roller 102 has returned
to its start position at time Tg the platen 106 would move
from its receiving position 112 to its load and unload position
108 and the cycle would be stopped ready forthe new medium 62
to be loaded in and the next image and transfer operation to
take place.
The toning station 18' is best illustrated in Figure 6. '.''
The toner feed roll 100 rotates with its bottom surface
submerged in the toner fluid 116 which is kept agitated by a .,
C - 15 -
.
- ~ ~3357 lL
submerged toner agitator 118 to keep the toner particles
from settling to the bottom o~ the tray or reservoir 56
The top of the toner feedroll is positioned approximately 5
to 10 microns from the bottom surface of the web 24. The
toner particles adhere to the periphery o~ the roll 100 as it
rotates through the fluid 116 and are attracted in the upper
position to the film portion of the web 24. The excess toner
fluid will be removed from the web 24 when it exits from the
toning platen 44 by the extractor roll 53 which is kept clean
by the squeegee 54~ The gap between the surfaces 50 and 52 . .
is also more clearly illustrated and is preferably on the
order of 5-40 mils with the extraction roll gap being
approximately 4 to 6 mils.
Figure 7 illustrates a third embodiment of the toning
station 18". In this embodiment a flexible sheet 120 is
connected to a pair o~ drive rolls 122 and 124. The rolls
122 and 124 are driven in tandem to rotate the sheet from
the roll 122 around a pair of guide rollers 126 and 128 onto .
the second drive roll 124 to apply toner to the film portion -~
as it passes through the toning station 18". The toning ~ :
platen 44, upper shoe 51 and the directional rolls 40 and 42 `
have been shown merely as illustrations and the flexible sheet
120 or window shade type toning station may also be used with
the embodiment as shown in Figure 4 with or without the toning ;
platen 44 and the upper shoe 51, depending on the tensi~ning
and positioning of the web 24. Once the film has passed
through the toning station 18" the drive rolls 122 and 124
reverse and rewind the flexible sheet or window shade 120 : :
16 -
. .
. . : - . . - . . - ....... .. : .-. ~.. . .... . . ... .
3;~s~
onto the roll 122. The toner may be picked up by the sheet
as it unwinds from the roll 122 or may be applied by a
mani~old like the manifold 46 of Figures 1 and 2 after it
has passed over the roll 126.
The design of the tonin~ manifolds 46 and 48 and the
air kni~e or air brush 80 is most clearly illustrated in
Figure 8, where the manifold 46 is shown in section. The
fluid air or toner is applied by a pump to one or a number
of ports 130 connected to a plurality of passageways 132
which direct the fluid into a first.chamber 134. The
chamber 134 as well as each of the succeeding chambers and
baffles extends the width of the manifold which is of a
width substantially equal to the imaged film portion of the
web 24. ~hen the fluid has filled the first cha~ber 134 it
will 1OW through a narrow passageway 136 into the second
chamber 138 in a serpentine fashion and from the chamber 138
through a passageway 140 into a third chamber 142 and in a
like manner from the third chamber 142 through a confining . .;
passage 144 to an exit or nozzle sli-t 146 in a smooth
nonturbulent even flow across the width of the nazzle 146
assuring a substantially constant even flow of taner across
the width of the web 24. The manifold 46 may be formed from ; .
a single block or may be ~ormed from an upper block portion ~
148 mated with a lower block portion 150 to form the;~.
passageways and chambers therebetween.
The toner preferably will not be applied across the entire ~:
width of the web 24 so that the back of the web will remain
dry for the motor 88 to frictionally drive the web through
- 17 - :
f
1~3;~S~l
one or more of the rolls. Pre~erably the roll 74 will be
driven as the web 24 makes a 180 wraparound this roll~
Each of the rolls is preferably made of metal to secure the
proper dimension and to make ohmic contact through the rolls.
36 and 38.
- 18 -
~/'`' ~
SUPPLEMENTAR~ L):~SCLOSURl
`- 1~ 57~L
An electrophotographic attachment as described in the
foregoing disclosure may be modified for use with an optical
projecting system for the purpose of making a copy of a document
on a sheet of carrier material, where the delivered produc-t is
not required to be used or converted to an offset prin-ting
plate. Such modification may involve the omission of the expo-
sure platen 32 and utilizing the rollers 36 and 38 to maintain
adequate tension of the web 24 so that the said web is placed
at the image plane of the camera system and lens 12. The
precision requiring use of the platen when an offse-t printing
plate is to be formed and delivered by apparatus 10 is not
required where the delivered product comprise mere copies of
the original subject matter.
The optical system may comprise a camera or may comprise
a light source, lens system and a shutter -to control the light
conditions for e~posure and for toning. ~
-19- :
~,'~'`', ~
~L33Sttl~L
Figure 9 is a clia~ram oE s-till another embodiment of the
toner s-tation to be used with the at-tachment.
- 20 -
. , _ . . ~ . . . . . . ..
~1 3~5~
Referring now to Figure 9, -tllere is ilLustratecl a fourth
embodiment of toning station 18'''. In tiliS embodimen-t, rollers
40, 42 and 60 of -the Figure l embodiment have been replaced
by a single roller 200 which is couple~ to the drive m~tor to
~unctionally drive belt 24. A reservoir 56' containing a supply
liauid toner LT is located below roller 200. Reservoir 56' in-
cludes an arcuate planar top surface 50' which is metallized,
has a transverse slot at the center and functions as a toning
platen 44'. The gap between top surface 50' and belt 24 is on
~he order of 5 to 40 mils. A toner feed roller lO0' is position-
ed so as to extend out slightly from the central slot in surface
50' and is mechanically coupled, by means not shown, to drive
roller 24. The space between feed roller lO0' and the bo-ttom
surface of web 24 is on the order of about 5 mils. In operation
toner LH is carried up from inside reservoir 56' by feed roller
lO0' to the space between toning platen top surface 50' and belt
24 and is attracted to the latent image on belt 24. A suitable
bias may be applied between surface 50' and belt 24 to assist in
the attraction of toner LT to the belt 24. Excess toner LT is
recaptured through suitably located openings in reservoir 56'.
- 21 -
.
