[0001] This invention relates to an apparatus for line-to-line recording of different color
component images.
[0002] Reproducing or copying color originals through a xerographic process has, in the
past, entailed the sequential production of three color separation images of the colored
original, with independent development thereof by cyan, magenta and yellow toners.
The images so formed are transferred onto the copy substrate material in registered
overlaying relationship, with the resulting composite color image being fused to provide
a permanent full color reproduction of the original.
[0003] In the aforedescribed color process, black is obtained through an amalgam of the
three color toners. However, it is often useful to provide a separate processing unit
devoted solely to black. This addition enhances machine versatility since it is then
possible to produce black and white copies directly and without the need to go through
the color separation cycle. The addition of a separate black processing unit also
enhances the quality and faithfulness of the black in color reproductions inasmuch
as black is formed directly using black toner rather than a combination of multi-color
toners.
[0004] However, while systems of the above type can provide full color reproductions, because
of the need to process three and possibly four color separation images for each copy,
the copy output is often very low. Where a single photoconductive drum is used for
example, normally each color separation image is created, developed, and transferred
to the copy substrate material before the next is started.
[0005] Where multiple photoreceptor processing units have been suggested to speed up copy
output, it has often been at the expense of greatly increased machine physical size
required to accommodate three and possibly four photoreceptor processing units. Attempts
to alleviate this problem and reduce machine size through the use of different diameter
photoreceptor drums or belts results in a system wherein a multiplicity of different
size photoreceptor drums or belts must be stocked for replacement purposes, it being
understood. that photoreceptor drums and belts are subject to fatigue and damage and
hence must be replaced from time to time.
[0006] The invention relates to an apparatus for line-to-line recording of different color
component images of a full color original on successive individual photoconductive
belts by means of controlled recording beams, each belt having an imaging station
for recording a different color component image, developers for developing the color
component images formed on each belt; an image transfer point on each belt where the
developed color component image on the belt is transferred successively to a copy
substrate material; a transport for bringing the substrate material into transfer
relation with the image transfer points; and drive means for driving the belts and
the transport, characterized by means supporting the belts so that the image transfer
points are in close proximity to one another, the distance between the imaging station
and the image transfer point of each succeeding belt being equal to the distance between
the imaging station and the image transfer point of the preceding belt plus the distance
from the image transfer point of the preceding belt to the image transfer point of
the succeeding belt to thereby assure transfer of the color component images in registered
superimposed relationship with one another to form a full color copy of the original.
[0007]
Figure 1 is a plan view of the color reproduction apparatus of the present invention;
Figure 2 is an enlarged view of one xerographic belt module illustrating details of
the vacuum belt tensioning mechanism;
Figure 3 is a schematic view showing. a color image signal generating means; and
Figure 4 is a plan view showing details of the imaging system for the color reproduction
apparatus of Figure 1.
[0008] Referring particularly to Fig. 1 of the drawings, there is shown the high speed four
color processor, designated generally by the numeral 10, of the present invention.
As will appear, processor 10 provides color or black and white copies of originals
on a suitable copy substrate material exemplified herein by copy sheets 12.
[0009] Processor 10 includes multiple xerographic type processing units 14, 16 and 18 for
processing color component images or separations which when combined produce full
color copies of color originals together with processing unit 20 for processing black
only. It will be understood that where black and white copies are desired, only processing
unit 20 need be activated.
[0010] Processing units 14, 16 and 18 process the three primary color components, namely
cyan, magenta, and yellow respectively in a manner understood by those skilled in
the art. It will be understood that processing unit 20 may be dispensed with and processing
units 14, 16 and 18 relied upon to provide black through the xerographic color process.
[0011] As shown in the drawings, the design and arrangement of processor 10 permits the
multiple processing units 14, 16, 18 and 20 to be disposed closely adjacent to one
another with the image transfer stations 68, 69, 70 and 71 thereof in close succession
along the copy sheet path.
[0012] A supply of copy substrate material, here shown as a stack 25 of copy sheets 12,
is provided in a suitable paper tray 27. A sheet feeder in the form of feed belt 30
entrained about roller pair 32 serves to advance the topmost sheet from stack 25 forward
into sheet inlet runway 34 of pneumatic sheet conveyor system 35. Suitable means (not
shown) are provided to incrementally elevate base 27
1 of tray 27 as sheets 12 are drawn off of the top of the sheet stack 25 to maintain
the topmost sheet of stack 25 in operative contact with feed belt 20.
[0013] Roller pair 32, which are rotatably supported by suitable journaling means (not shown),
are drivingly coupled to a suitable step motor 36. Motor 36, when actuated, rotates
roller pair 32 for a predetermined interval in the direction shown by the solid line
arrow to drive feed belt 30 and advance the topmost sheet on stack 25 forward into
sheet inlet runway 34 and the nip of rollers 38, 39 of tri-roller inverter 42. Gate
41 restricts feeding of sheets from sheet stack 25 to one sheet at a time.
[0014] Pneumatic sheet conveyor system 35 includes sheet inlet runway 34, feeder runway
45, duplex return runway 46, inverter runway 47, and copy discharge runway 48, each
runway comprising a closed chute-like passage 54 for copy sheets bounded by upper
and lower walls 50, 51 and side walls 52. When communicated with a relatively low
pressure air stream, copy sheets introduced into the runways 34, 45, 46, 47 and 48
are carried therewithin in the direction of air flow. As will appear, runways 34,
45, 46, 47 and 48 are operatively coupled together to form together with copy sheet
transport belt 55, a transport or conveyor system for copy sheets 12.
[0015] A four way junction 57 couples sheet inlet runway 34, sheet feeder runway 45, duplex
return runway 46, and inverter runway 47 together. Copy sheets advanced by feed belt
30 pass through inlet runway 34 via junction 57 to sheet feeder runway 45, runway
45 leading to and exiting adjacent to copy transport belt 55. Sheet feeder runway
45 includes an air inlet 59 in communication with air supply duct 60 for introducing
transporting air into the copy sheet conveyor system. A sheet register comprised of
roller pair 62, 63 adjacent the discharge end of runway 45 serves to engage and register
the copy sheets therewithin with the images in process by developing units 14, 16,
18 and 20. Rollers 62, 63 are driven from main drive motor 65 in unison with copy
transport belt 55 and with photoconductive belts 110 of processing units 14, 16, 18
and 20.
[0016] Copy transport belt 55 comprises an endless perforated belt of suitable flexible
material stretched about rotatable vacuum idler and driving drums 66, 67 respectively,
Drums 66, 67 are rotatably supported by suitable journaling means (not shown). Driving
drum 67 is driven by main motor 65 in the direction shown by the solid line arrow.
Drums 66, 67 are hollow and have perforations 68 about the periphery thereof to permit
sub-atmospheric pressure to be applied via the perforated copy transport belt 55 to
tack copy sheets 12 thereto. The interior of drums 66, 67 communicate with a suitable
source of sub-atmospheric pressure (not shown). Guide rollers 90, 91 guide belt 55
through a relatively sharply curved path downstream of drum 67 to facilitate separation
of copy sheets 12 therefrom and into the nip formed by rollers 76, 77 of fuser 75.
Guide rollers 90, 91 are rotatably supported by suitable journaling means (not shown).
[0017] To facilitate transfer of the copy sheets from sheet feeder runway 45 to copy transfer
belt 55, the lower wall of runway 45 is extended at 51'. Extension 51' has a configuration
complementary to the arcuate shape of drum 46.
[0018] A succession of image transfer stations 68, 69, 70, and 71, each associated with
a belt module 14, 16, 18 and 20 respectively, are disposed in close proximity to one
another along the portion of copy transport belt 55 laying between drums 46, 47, belt
modules 14, 16, 18, and 20 being disposed such that the uppermost portion of the photoconductive
belt 110 is in predetermined pressure contact with transport belt 55.
[0019] A transfer corotron 73 is provided opposite each belt module 14, 16, 18, and 20 and
interior of copy transport belt 55. Corotrons 73 serve to transfer the images developed
on their respective belts 110 onto copy sheets 12 as the sheets are transported therepast
by copy transport belt 55, such transfer taking place in accordance with well known
principles of xerography. Where multi-color copies are being produced, the color component
images are transferred in registered superimposed relation.
[0020] Following transfer of the developed image or images onto copy sheets 12, the sheets
are carried by copy transport belt 55 to a fuser 75 whereat the images are fixed by
heat. Fuser 75.comprises an upper heated fuser roll 76 cooperating lower pressure
roll 77 in driving engagement with one another. Fuser rolls 76, 77 are drivingly connected
to motor 65, motor 65 rotating rolls 76, 77 in the direction indicated by the solid
line arrow.
[0021] A pneumatic junction 79 is provided downstream of fuser 75, junction 79 leading to
duplex return runway 46 and to copy discharge runway 48 of pneumatic sheet conveyor
system 35. Deflector gate 80 in junction 79 serves to selectively route copy sheets
leaving fuser 75 into either runway 46 or 48.
[0022] Copy discharge runway 48 conveys the copy sheets bearing the fused image to a copy
output station, exemplified herein by copy tray 82, wherein the finished copies are
accumulated. Roller pair 83, 88 facilitate discharge of the copy sheets from copy
discharge runway 48 into the tray 82. While the copy output station is illustrated
as comprising a copy tray, other types of copy output stations, i.e., a sorter, may
be contemplated.
[0023] Copies routed by deflector gate 80 into duplex return runway 46 are carried back
to junction 57 where the copies are inverted to permit a second image to be formed
on the unused side thereof. For this purpose, the copy sheets are passed by junction
57 and roller pair 39, 40 of tri-roller inverter 42 into deadend inverter runway 47.
It will be understood that rollers 38, 39, and 40 of tri-roller inverter 42 are supported
for rotation by suitable journaling means (not shown) and are driven by motor 65 in
the direction shown by the solid line arrow.
[0024] As the trailing edge of a copy sheet exits from the nip of rollers 39, 40, the sheet
trailing edge is carried by roller 39 downwardly and effectively directed into the
nip of rollers 38, 39. Rollers 38, 39 in cooperation with the flow of transporting
air reverse the direction of sheet movement and more the now inverted sheet into sheet
feeder runway 45 for a second pass through the processing apparatus.
[0025] Duplex return runway 46 and sheet discharge runway 48 are provided with air inlets
at 84 for communication with transporting air supply duct 60.
[0026] Processing units 14, 16, 18, and 20 each comprise a complete xerographic sub-assembly,
the principle processing elements of which comprise a charging station 101, exposure
station 103, developing station 104, cleaning station 105, and transfer station (the
latter having been previously identified by numerals 68, 69, 70, and 71) in operative
disposition about an endless photoconductive belt 110 supported on a belt module 111,
112, 113, and 114 respectively.
[0027] Referring particularly to Fig. 2, belt modules 111, 112, 113, 114 each comprise a
generally triangular shaped support frame 115 having photoconductive belt support
rollers 116, 117, and 118 mounted thereon at the apices of the triangle. Rollers 116,
117 and 118 are supported for rotation about fixed axes in frame 115 by means of suitable
bearings (not shown) with roller 118 thereof being drivingly coupled to main motor
65. Belt module frames 115 are each recessed internally in varying degrees at 120.
A hollow sub-atmospheric or vacuum chamber 122 is formed within the confines of each
frame 115 by the frame side and end walls 124, 125 respectively, and by upper and
lower frame cross members 126, 127 respectively, chamber 122 extending across the
width of the respective belt.modules. A transverse opening or port 128 in lower frame
cross member 127 communicates vacuum chamber 122 with recessed portion 120 thereof.
The interior surfaces of frame side walls 124 are suitably beveled at 131, 132 to
provide side support to the loop portions 135 of photoconductive belts 110 formed
therein during operation. Pressure relief ports 136 in end walls 125 permit ingress
of air to enable the requisite belt attracting air flow patterns to be generated.
[0028] To assure registration of succeeding color component images with the preceding image
or images, the belt modules 112, 113, 114 are sized so that the length L of the belt
run from exposure station 103 to transfer stations 69, 70, 71 thereof is equal to
the lenght L of the preceding belt module 111, 112, 113 plus the distance d. from
the transfer station 68, 69 or 70 of the preceding belt module 111, 112, 113 respectively
to the transfer station.69, 70 or 71 of the succeeding belt module 112, 113, 114 respectively.
[0029] Photoconductive belts 110 comprise any suitable photoconductor material such as selenium
supported on a suitable flexible substrate or backing, such as myler. To promote serviceability
and reduce cost, the photoconductive belts 110 for all belt modules 111, 112, 113,
114 are the same size, with an overall length greater than the minimum belt run formed
by belt modules 111, 112, 113, 114.
[0030] To accommodate the aforedescribed spatial relationship between successive belt modules
while permitting interchangeable belts 110 to be used, the depth of the recess 120
for each belt module 111, 112, 113, l14 varies. In the arrangement shown, recess 120
of belt module 111 is largest with the recesses 120 of the succeeding belt modules
112, 113 and 114 being progressively smaller. As a result, the size of the belt loop
135 established in the several recesses during operation of the system 10 is progressively
smaller with each successive belt module 111, 112, 113, 114. Evacuation of chamber
122 while processing copies creates a pressure differential across the segment of
the photoconductive belt 110 adjacent the belt module recesses 120 which draws the
belt segment into the recess to form belt loop 135 and tension the photoconductive
belts about rollers 116, 117, 118 of belt modules 111, 112, 113, 114.
[0031] Developing stations 104 comprise any suitable image developing devices. Developing
stations 104 are exemplified herein by a developer housing 150 having pickup roll
152 and magnetic or mag brush type intermediate feed and developer rolls 154, 155
respectively housed therewithin. The lower portion of developer housing 150 forms
a sump 157 for the supply of developing material, pickup roll 152 being in operative
disposition therewith in sump 157. Pickup roll 152 has a succession of cavities 158
in the periphery thereof for transporting developing material from sump 157 into operative
juxtaposition with intermediate feed roll 154.
[0032] Developing material from pickup roll 152 is magnetically attracted to the surface
of feed roll 154 by the magnetic field created by magnets 159 thereof, resulting in
the formation of a developer blanket 160. Following trimming thereof by trim bar 162,
the blanket of developing material is carried upwardly by roll 154 to developer roll
155. Developer roll 155, in turn, carries the developer, attracted thereto by magnets
163 thereof, into operative relation with the surface of photoconductive belt 110
at developing station 104. Rolls 152, 154, 155 of developing stations 104 are rotatably
supported in developer housing 150 thereof by suitable journaling means (not shown)
and are driven in the direction shown by the solid line arrows by main motor 65.
[0033] Cleaning stations 105 each comprise, in the exemplary arrangement shown, a rotatable
cleaning brush 165 disposed in housing 166, brush 165 being supported for rotation
by suitable journaling means (not shown) such that bristles 167 thereof are in wiping
contact with the surface of photoconductive belt 110. Cleaning brush 165 is driven
by main motor 65. Leftover developing material and any other debris, removed from
belt 110 by brush 165 is carried from housing 166 by means of suction, the lower portion
of housing 166 being connected to vacuum exhaust duct 168 for this purpose.
[0034] Digital signals representing the primary color separations, i.e. red, green, and
blue, of-a colored original to be reproduced, together with black may be provided
in any suitable manner. For example, and referring to Fig. 3, a colored original 200,
which is disposed upon a suitable support such as platen 201, may be scanned by a
conventional video type color camera 203. The color output signals of camera 203 are
fed through input channels 204, 205, 206 to a suitable matrix control network 210
wherein the signals may be optimized in accordance with predetermined algorithms.
The resulting color separation signals are stored in a suitable memory 213 under the
direction of computer 212 pending use.
[0035] Network 210 additionally generates digital signals representing the fourth color
image i.e. black. The black image signals are obtained through comparative analysis
of the red, green, and blue color separation signals in accordance with a predetermined
algorithm. The black image signals are fed to memory 213 through input channel 207.
[0036] Referring to Fig. 4 of the drawings, a flying spot type imaging system is thereshown
effective to provide image rays representative of the three primary color separations
and black at exposure stations 103 of developing units 14, 16, 18, 20 in repsonse
to the image signals stored in memory 213. For this purpose, a suitable source of
light, i.e. laser 222 is provided. The light beam 223 produced by laser 222 is directed
by mirror 224 through lens 225 and into four faceted mirror 226. Mirror 226 divides
the beam 223 into four distinct light beams 230, 231, 232, 233 which, through the
action of lens 225, are focused at four channel acousto-optical modulator 228.
[0037] The color separation image signals, together with the black image signals in morory
213 are inputed to the respective beam control gates 240, 241, 242, 243 of modulator
228, along signal output channels 244, 245, 246, 247. It will be understood that the
image signals stored in memory 213 are addressed by computer 212 in synchronism with
the operating speed of the reproduction system 10.
[0038] As will be understood by those skilled in the art, the individual control gates 240,
241, 242, 243 of modulator 228 respond to the binary state (i.e. "1" or "0") of the
image signals applied thereto through channels 244, 245, 246, 247 respectively to
direct the light beams 230, 231, 232, 233 associated therewith either toward a suitable
beam stop 255 or toward the individual facets 257 of four faceted mirror 258. Beam
stop 255 intercepts light directed thereagainst to block further passage thereof.
[0039] Light striking mirror 258 is reflected therefrom to expander lens 260 which restores
the light into four parallel paths 261, 262, 263, 264. It is understood that the discrete
light patterns along the parallel light paths 261, 262, 263, 264 are representative
of the three color separation images and black comprising the full color original
200. From lens 260, the now parallel light paths are directed by mirror 265 onto the
facets 266 of rotating scanning polygon 267. Polygon 267 is rotated by motor 268 .
at a speed proportional to the movement of photoconductive belts 110.
[0040] The multiple scanning light paths 261, 262, 263, 264 reflected from facets 266 of
polygon 267 are focused by main imaging lens 270 onto the surface of photoconductive
belts 110 at imaging stations 103 of the processing units 14, 16, 18, 20. A triangular
shaped four faceted mirror 271 routes the light paths into separate branches 261',
262', 263', 264' leading to the various imaging stations 103, branches 261', 264'
being routed by single mirrors 273 to the imaging stations of processing units 14
and 20 while branches 262', 263' are routed by three mirror combination 274 to the
imaging stations of processing units 16 and 18.
[0041] In operation of processing system 10, the light beam generated by laser 222, which
serves as the exposure medium for the photoconductive belts 110, is broken up into
four independent paths 261, 262, 263, 264, one for each exposure station 103 of processing
units 14, 16, 18, 20. The continuity of the four light beams 230, 231, 232, 233 is
controlled in accordance with the image signals from memory 213 through acousto-optical
modulator 288. The imaging beams scan or traverse across the photoconductive belts
at imaging stations 103 from edge to edge, with each photoconductive belt 110 being
exposed simultaneously.
[0042] Prior to exposure of the photoconductive belts 110, the source of vacuum (not shown)
for vacuum chambers 122 of belt modules 111, 112, 113, 114 is energized to draw the
excess portion of belts 110 into the recessed areas 120 and tension the belts. Main
motor 65 is energized to drive photoconductive belts 110 and operate the several xerographic
processing components, i.e. developing station 104, associated therewith. Power is
supplied to charge and transfer corotrons 102, 73 respectively, the former serving
to place a uniform electrostatic charge on belts 110 in preparation for imaging. The
source of pressure air to air supply ducts 60 of pneumatic sheet conveyor system 35
is energized.
[0043] At a predetermined time during the copying cycle, step motor 36 is actuated to drive
sheet feed belt 30 and advance the topmost sheet 12 in tray 27 forward into the sheet
inlet runway 34 and the nip of rolls 38, 39. The sheet is carried into sheet feeder
runway 45 with the leading edge thereof registered by register roll pair 62, 63 with
the leading edge of the color separation images developed on photoconductive belts
110.
[0044] Exposure of the charged photoconductive belts 110 at exposure stations 103 selectively
discharges the belt in accordance with the light pattern applied thereto to create
latent color separation electrostatic images on each photoconductive belt 110. The
latent electrostatic images so produced are developed by the respective cyan, magenta,
yellow and black developers of processing units 14, 16, 18, 20 to form the four color
separation images. The developed separation images are transferred in succession at
image transfer stations 68, 69, 70, 71 to the copy sheet carried therepast by copy
transport belt 55. The copy sheet, bearing the composite color image, is carried to
fuser 75 whereat the color image is fixed. The copy sheet may be thereafter transported
via copy discharge runway 48 to output tray 82 or where a second or duplex image is
desired on the unused side thereof, returned to the sheet feeder runway 45 via duplex
return runway 46 and inverter runway 47.
[0045] While the invention has been described with reference to the structure disclosed,
it is not confined to the details set forth, but is intended to cover such modifications
or changes as may come within the scope of the following claims:
1. In an apparatus for line-to-line recording of different color component images
of a full color original on successive individual photoconductive belts (110) by means
of controlled recording beams (261', 262', 263', 264') wherein recording of different
color component images takes place at imaging stations associated with said belts;
developing means (155) for developing the color component images formed on said-belts;
a transfer point associated with each of said belts whereat the developed color component
images on said belts are transferred to a copy substrate material (12) in succession;
transport means (35, 55) for bringing said substrate material into transfer relation
with said belt transfer points; and
drive means (65) for driving said-belts and said transport means, characterized by:
means (116, 117, 118, 122) for operatively supporting said belts with the transfer
points in close proximity to one another, the distance (L) between the imaging station
and the transfer point of each succeeding belt being equal to the distance (L) between
the imaging station and the transfer point of the preceding belt plus the distance
(D) from the transfer point of the preceding belt to the transfer point of the succeeding
belt whereby to assure transfer of said color component images in registered superimposed
relationship to form a full color copy of said original.
2. The apparatus according to claim 1 characterized by belts of equal length.
3. The apparatus according to claim 2 characterized by plural rotatably mounted belt
supporting rolls (116, 117, 118) forming a belt run for each of said belts, the length
of each belt being greater than the belt runs formed by said rolls, and vacuum tensioning
means (122) operative to draw each belt inwardly to tension the belt about the supporting
rolls.
4. The apparatus according to claim 3 characterized by a first belt supporting roll
(118) adjacent each imaging station and a second belt supporting roll (116) adjacent
each transfer point, cleaning means (116) upstream of each imaging station for removing
residual developer from each belt prior to recording a new color component image,
a third belt supporting roll (117) adjacent each cleaning means, said vacuum tensioning
means (122) being disposed between said first and third belt supporting rolls.
5. The apparatus according to claim 1 characterized by means forming a path for said
copy substrate material, and a generally triangular photoconductive belt module associated
with each of said recording beams, each of said belt modules including an endless
photoconductive belt with means for supporting said belt for operative movement in
an endless path, said belt modules being positioned in closely spaced side-by-side
relationship with one apex of each of said belt modules in operative disposition with
said copy substrate path at said transfer points at minimally spaced intervals therealong.
6. The apparatus according to claim 5 characterized by said developing means including
a developing device associated with each of said belts, said developing devices being
disposed at a second apex of each belt to facilitate disposition of said belt modules
in close side-by-side relationship.
7. The apparatus according to claim 5 characterized by developing means including
a developing device associated with each of said belts at a developing station, the
imaging and developing stations being disposed opposite second and third apices of
said belt module respectively to facilitate disposition of said belt modules in close
side-by-side relationship.
8. The apparatus according to claim 1 in which said belt supporting means is characterized
by at least two rotatable spaced apart belt supporting rolls, said rolls defining
a belt run therebetween;
means (65) for drivingly rotating at least one of said rolls (118);
an endless photoconductive belt disposed over said rolls, the length of said belt
being greater than the length of the belt run defined by said rolls;
means forming a vacuum chamber (122) interior of said belt run; and
means for evacuating said chamber to draw the excess length of said belt into said
chamber whereby to form a U-shaped belt loop (135) while tensioning said belt to provide
operative engagement with said rolls.
9. The apparatus of claim 8 characterized by said vacuum chamber having predetermined
air escape ports (136) on either side of said belt to control vacuum force on said
belt.
10. The apparatus of claim 8 characterized by said evacuating means having control
means for regulating the size of said belt loop and tension on said belt.