Copy sheet positioning apparatus

Copy sheet positioning apparatus is provided in electrographic apparatus which produces copies of at least first and second dimensions and which includes a movable image transfer member upon which transferable unfixed images are formed. The copy sheet positioning apparatus includes a first sheet handling assembly located adjacent to the image transfer member which defines a first path for a copy sheet of a first dimension. The first sheet handling assembly is operative to remove and reposition such a copy sheet with respect to the image transfer member. The copy sheet positioning apparatus also includes a second sheet handling assembly which defines with the first sheet handling assembly a second path for a copy sheet of a second dimension. The second sheet handling assembly cooperates with the first sheet handling assembly to remove and reposition such a copy sheet with respect to the image transfer member.

BACKGROUND OF THE INVENTION 
This invention relates generally to electrographic apparatus and more 
particularly this invention relates to electrographic apparatus which 
produces copies of at least first and second dimensions. 
Many techniques have been proposed for producing copies in which a 
plurality of images are produced on a single sheet. In one such technique, 
color separation images of an original are superimposed upon a sheet to 
produce a color copy of the original. An electrographic apparatus for 
producing colored copies is described and illustrated in commonly assigned 
U.S. Pat. No. 4,251,154, issued Feb. 17, 1981, for "Electrophotographic 
Color Copier," by M. J. Russel. The described apparatus includes a movable 
image transfer member for receiving related transferable color separation 
images in non-overlapping image areas. The image transfer member is moved 
along a transport path and a transfer mechanism is mounted adjacent to the 
transport path for transferring at spaced locations along the path the 
color separation images to a receiver sheet. The transfer mechanism 
successively positions the receiver sheet at the spaced locations in 
register with and in image transfer relation to the color separation 
images on the moving transfer member to superimpose the color separation 
images in register on the receiver sheet. Although the disclosed apparatus 
may be suitable for the purposes for which it was intended, the apparatus 
is limited to producing copies of a single dimension as measured in the 
direction of movement of the image transfer member. A receiver sheet is 
removed from the image transfer member and positioned in contact with the 
transfer member in registration with a successive image on the transfer 
member by means of a fixed dimension register roller which has a 
circumference equal to the dimension of one image area in the direction of 
travel of the image transfer member plus the distance between adjacent 
areas. Thus, for example, if letter size copies (81/2.times.11 inches) and 
legal size copies (81/2.times.14 inches) are produced, the circumference 
of the register roller is equal to 81/2 inches plus an interframe distance 
of approximately 11/2 inches or a total of 10 inches. 
If it is desired to produce copies of greater dimension, for example, 
11.times.17 copies, then both the circumference of the register rollers 
and the image area on the image transfer member would have to be increased 
in size. However, if it were desirable to produce both 81/2.times.11 and 
11.times.17 inch copies with the larger sized apparatus, then certain 
inefficiencies in operation of such an apparatus would result. Thus, if 
such an apparatus were switched from producing larger copies to smaller 
copies, the register roller must be accelerated to reposition the copy 
sheet in time for the 81/2.times.11 image. This change in roller velocity 
results in increased power requirements for the registration roller drive, 
in registration inaccuracies, and in mechanical difficulties such as 
vibration. Alternatively, if the register roller is not accelerated, an 
81/2.times.11 image produced after an 11.times.17 image must be delayed on 
the image transfer member, thus creating an unusually large interframe 
distance. This results in decreased productivity since the maximum 
productivity would be limited to the number of large frames imaged per 
hour. 
Thus, it would be desirable to provide an electrographic apparatus which 
not only produces multiple images on a single copy but also which 
efficiently produces copies of different dimensions. 
SUMMARY OF THE INVENTION 
According to the present invention, copy sheet positioning apparatus is 
provided in electrographic apparatus which produces copies of at least 
first and second dimensions and which includes a movable image transfer 
member upon which transferable unfixed images are formed. The copy sheet 
positioning apparatus includes a first sheet handling means located 
adjacent to the image transfer member for defining a first path for a copy 
sheet of said first dimension. The first sheet handling means is operative 
to remove a copy sheet of said first dimension from transferable 
relationship with said image transfer member after transfer of one unfixed 
image to said sheet and to reposition said copy sheet in transferable 
relationship with a successive unfixed image on said image transfer member 
wherein said removing and positioning is effected without contacting the 
first unfixed image on the copy sheet. 
The copy sheet positioning apparatus also includes second sheet handling 
means for defining with said first sheet handling means a second path for 
a copy sheet of said second dimension. The second sheet handling means 
cooperates with said first sheet handling means to remove a copy sheet of 
said second dimension from transferable relationship with said image 
transfer member after transfer of one unfixed image to said copy sheet and 
to reposition said copy sheet in transferable relationship with a 
successive unfixed image on said image transfer member wherein said 
removing and repositioning is effected without contacting said first 
unfixed image on said copy sheet. 
The invention and its objects and advantages will become more apparent in 
the detailed description of the preferred embodiment presented below.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown in FIG. 1, there is schematically illustrated electrographic 
apparatus in which a preferred embodiment of sheet positioning apparatus 
according to the present invention is incorporated. The electrographic 
apparatus is operable to produce copies of different dimensions in which a 
plurality of superimposed images are formed on a copy. As shown, 
electrographic apparatus 10 includes a flexible image transfer member or 
photoconductive belt 12 trained about rollers 14, 16, 18, 19, 20, and 22. 
Belt 12 is moved in a clockwise direction by means of a drive motor 24 
which is linked to roller 22. Belt 12 has a plurality of sequentially 
spaced non-overlapping image areas which pass successively through a 
series of electrophotographic processing stations located along the path 
of belt 12. Belt 12 preferably includes timing marks such as regularly 
spaced perforations 25 (FIG. 4A) which are sensed by sensor 26 to provide 
timing signals to logic and control unit 28. Logic and control unit 28 
includes a microprocessor such as model 8085 available from the Intel 
Corporation of California. An encoder 30 is also linked to roller 22 and 
produces timing signals for LCU 28 which are used with the timing signals 
from sensor 26 to control the operation of electrographic apparatus 10. 
Transferable images are formed on belt 12 through the steps of charging, 
exposing, and developing. As shown in FIG. 1, a corona charger 32 applies 
a substantially uniform electrostatic charge on belt 12. At exposure 
station 34 a light image of an original image is projected onto the 
charged belt to discharge those areas struck by light to form a latent 
electrostatic image corresponding to the original image. In apparatus 10, 
related color separation latent electrostatic images are formed 
sequentially and in spaced relation on belt 12 by exposing an original 36 
moved onto transparent platen 38 by means of feed rollers 40 and 42 or 
recirculating document feeder 44. 
Where a four-color original is to be reproduced, four sequential latent 
electrostatic images are formed on belt 12 by successively illuminating 
document 36 by means of xenon flash lamps 46 and 48 to produce light 
images which are projected upon belt 12 at exposure station 34 by means of 
mirrors 50 and 52 and projection optics 54. Projection optics 54 are 
movable in order to permit enlarged or reduced images of the original 
document 36. The document 36, for example, is illuminated four successive 
times to produce four related latent electrostatic separation images by 
successively inserting into light path 56, neutral density filter 58, red 
filter 60, green filter 62, and blue filter 64. Filters 58, 60, 62, and 64 
are sequentially activated by solenoids 66, 68, 70, and 72 respectively, 
which are selectively actuated by LCU 28. Thus, latent electrostatic 
images corresponding to black, red, green and blue separation images are 
sequentially formed on belt 12 to be developed at developer station 74. 
Development station 74 has a plurality of magnetic brush toning stations 
which are adjacent to but spaced from the path of belt 12. Thus, for 
four-color reproduction four magnetic brush toning stations are provided. 
Developer station 74 includes (1) black station 76 containing black toner 
particles to develop the black electrostatic latent image, (2) cyan toning 
station 78 containing cyan toner particles which are complementary in 
color to develop the red electrostatic latent image; (3) magenta toning 
station 80 containing magenta toner particles which are complementary in 
color to develop the green electrostatic latent image; and (4) yellow 
toning station 82 containing yellow toner particles which are 
complementary in color to develop the blue electrostatic latent image. 
Backup rollers 84, 86, 88, and 90 are located on the opposite side of belt 
12 and are selectively activated by solenoids 92, 94, 96, and 98 through 
control of LCU 28. 
When one of rollers 84, 86, 88, and 90 is moved into contact with belt 12, 
belt 12 is deflected from its normal path into operative enegagement with 
a respective magnetic brush so that charged toner particles of the engaged 
magnetic brush are attracted to the oppositely charged latent 
electrostatic image to develop the latent image into a transferable 
unfixed toner image. Thus, as the black electrostatic latent image 
approaches developer station 76, LCU 28 actuates solenoid 92 to move 
roller 84 to deflect belt 12 so that the black image is developed by black 
toner particles brought up into contact with belt 12 by magnetic brush 
toning station 76. As soon as the black separation image leaves the area 
of station 76, solenoid 92 retracts roller 84 so that belt 12 returns to 
its non-deflected path. Similar operating cycles for stations 78, 80, and 
82 are effected, so that the red latent electrostatic image is developed 
only with cyan toner particles, the green latent electrostatic image is 
developed only with magenta toner particles and the blue latent 
electrostatic image is developed only with yellow toner particles. 
After the developed toner images leave developer station 74, belt 12 is 
irradiated by post-development erase lamp 100 to reduce the electrostatic 
attraction between the toner image and the photoconductive belt. 
In one mode, apparatus 10 is operable to produce copies of standard office 
sizes such as 81/2.times.11 inches and 81/2.times.14 inches so that the 
short dimension, for example, 81/2 inches, is oriented in the direction of 
belt movement in order to increase productivity. Belt 12 has a width which 
is sufficient to contain an image of the longest copy to be produced. 
Thus, if 14-inch copy is the longest copy produced, belt 12 has a width of 
approximately 16 inches and would contain a series of non-overlapping 
image frames each having a first dimension of L.sub.1 (FIGS. 4A, 4B) in 
the direction of movement of belt 12. L.sub.1 is the sum of the image 
width plus an interframe distance between copies; e.g., for an image width 
of 81/2 inches and an interframe distance of 11/2 inches, L.sub.1 equals 
10 inches. The length of belt 12 is equal to the number of image frames 
times L.sub.1 ; e.g., a six-frame belt would have a 60-inch length. 
In a second mode, apparatus 10 is operable to produce copies having widths 
of double the normal copy width such as used in books and magazines. This 
mode is illustrated in FIGS. 4C and 4D where belt 12 is divided into a 
series of image frames having a second dimension L.sub.2 which is large 
enough to produce copies of double copy size such as 17 by 11 inches (FIG. 
4C) and 17 by 14 inches (FIG. 4D) with an interframe distance I.sub.2 of 3 
inches. Thus, the image frame for the larger copies is double the size of 
the image frame for the smaller copies; i.e., instead of six image frames, 
belt 12 would have three image frames. In the second mode, LCU 28 is 
programmed to skip every second perforation 25 on belt 12 to control 
operation of apparatus 10. 
Apparatus 10 is provided with a frist supply 102 of copy sheets of a first 
dimension such as 81/2.times. 11 and a second supply 104 of copy sheets of 
a second dimension such as 17.times.11. An operator-selectable sheet size 
switch on control and display panel 106 provides a signal to logic and 
control unit 28 to feed either a copy sheet of the first dimension from 
tray 102 or copy sheet of a second dimension from supply 104. For purposes 
of illustration, it will be assumed that the operator has pressed a switch 
on panel 106 to produce copy sheets of 81/2.times.11 size. In such case, a 
vacuum feed roller 108 will separate a sheet 110 from supply 102 and move 
it into engagement with registration mechanism 112. Mechanism 112 releases 
the copy sheet in timed relationship with the first toner image on belt 12 
in advance of transfer station 114 which includes transfer charger 118 and 
detack charger 116. As the copy sheet passes under charger 118, a charge 
opposite to the charge of the toner image is applied to the back of sheet 
110 to transfer the first (black) electrostatic image from belt 12 to one 
side of sheet 110. Sheet 110 and belt 12 then move under detack corona 
charger 116 which neutralizes the charge on sheet 110 so that it may be 
easily separated from belt 12. 
In order to register copy sheet 110 with the second (cyan) toner image on 
belt 12, the sheet bearing the black toner image is removed from 
transferable relationship with belt 12 and is repositioned in transferable 
relationship with the next successive toner image on belt 12. In order to 
effect removal and repositioning, according to the present invention, 
there are provided a plurality of copy sheet positioning apparatus spaced 
along belt 12 between transfer stations. Thus, copy sheet positioning 
apparatus 120 according to the present invention is located adjacent to 
belt 12 opposite roller 16 between transfer stations 114 and 122; copy 
sheet positioning apparatus 158 is located adjacent to belt 12 opposite 
roller 18 between transfer stations 122 and 161; and copy sheet 
positioning apparatus 168 is located adjacent to belt 12 opposite roller 
19 between transfer stations 161 and 172. Copy sheet positioning apparatus 
120, 158 and 168 are similar in construction and operation. 
Copy sheet handling apparatus 120 includes a first sheet handling assembly 
for defining a first path for a copy sheet of a first dimension and a 
second copy sheet handling assembly operating cooperatively with the first 
sheet handling assembly for defining a second sheet path for a copy sheet 
of a second dimension. In the copy sheet positioning apparatus 120, first 
sheet handling assembly includes a vacuum roller 124 spaced from belt 12 
which is dimensioned to have a circumference equal to the length of image 
frame L.sub.1 and which defines a first path 126 around the periphery of 
roller 124. A second copy sheet path 128 has a length equal to the 
dimension of image frame L.sub.2 and comprises a second copy sheet 
handling assembly including vacuum roller 130 and movable plenum 132 and 
fixed plenum 134 located between vacuum rollers 124 and 130. When a copy 
sheet 110 of the first dimension is processed, plenum 132 is moved by 
solenoid 136 to an open position out of intersection with first path 126 
(FIG. 3). 
As illustrated in greater detail in FIG. 3, when the leading edge of copy 
sheet 110 is positioned immediately adjacent to vacuum roller 124, it is 
tacked to roller 124 by means of a vacuum applied to plenum 138 of roller 
124 from vacuum source 140 over conduit 142. As roller 124 rotates, vacuum 
applied from source 140 over lines 144 and 146 to plenums 148 and 150, 
respectively, move sheet 110 around first path 126 so that it is 
repositioned in transferable relationship with the next (cyan) toner image 
on belt 12. Sheet 110 is then detacked from roller 124 by interrupting the 
vacuum applied to plenums 138. 
Sheet 110 then travels along with belt 12 to second transfer station 122 
where second corona transfer charger 157 transfers the cyan toner image to 
sheet 110 in registration with the previously transferred black toner 
image. Second detack corona charger 159 then neutralizes the charge on 
sheet 110 so that vacuum roller 156 (which is spaced from belt 12) of 
second copy sheet handling apparatus 158 can remove sheet 110 from 
transferable relationship with belt 12 and move it around path 160 back 
into transferable relationship with the third (magenta) toner image. Copy 
sheet 110 then moves with belt 12 under a third transfer corona charger 
162 which transfers the magenta toner image onto sheet 110 in registration 
with the previously transferred black and cyan toner images. Detack 
charger 164 neutralizes the charge on sheet 110 so that sheet 110 may be 
removed from transferable relationship with belt 12 by means of vacuum 
roller 166 (spaced from belt 12) of third copy sheet positioning apparatus 
168. Roller 166 moves sheet 110 around path 170 and repositions sheet 110 
in transferable relationship with the fourth (yellow) and last toner image 
on belt 12. Sheet 110 then travels with belt 12 to fourth transfer station 
172 where fourth transfer corona charger 174 transfers the yellow toner 
image onto sheet 110 in registration with the black, cyan and magenta 
toner images. Fourth detack charger 176 neutralizes the charge on sheet 
110 so that it is separated from belt 12 at roller 120 and transported by 
means of vacuum transport 178 into the nip formed by fuser rollers 180 and 
182 to fuse the superimposed toner images to sheet 110. Sheet 110 is then 
fed into output tray 184. 
A cleaning station 186 is provided to effect mechanical and electrical 
cleaning of photoconductive belt 12. Station 186 includes a cleaning 
assist erase lamp 188 which exposes photoconductive belt 12 to radiation 
to substantially reduce any charge remaining on belt 12; a cleaning assist 
charger 190 which impresses an alternating current charge on belt 12 to 
neutralize the charges on untransferred toner particles; and a brush 192 
to remove any residual toner from belt 12 so that belt 12 is ready for 
another electrophotographic cycle. 
When copies of a second dimension are produced by apparatus 10, the charge, 
expose, and development steps described above will produce a sequence of 
toner images on image frames L.sub.2 of belt 12. A copy sheet 194 of a 
second dimension (e.g., 17.times.11 inches) is fed from supply 104 to 
registration mechanism 196 which registers sheet 194 with the first toner 
image on belt 12. Transfer of the first toner image to sheet 194 is 
effected by transfer charger 118 and the charge on sheet 194 neutralized 
by detack charger 116. 
Copy sheet positioning apparatus 120 operates to move sheet 194 around 
second path 128. 
Referring to FIG. 2, solenoid 136 has been actuated by LCU 128 to move 
plenum 132 to a closed position. Stepper motor 198 is linked to rollers 
124 and 130 and causes them to rotate in a counterclockwise direction. LCU 
28 also causes vacuum source 140 (FIG. 3) to apply a vacuum over conduits 
146 and 142 to plenums 138 and 150 of roller 124 but not to plenum 148. 
Vacuum source 140 also applies vacuum to plenums 132 and 134 respectively 
over conduits 200 and 202 and to plenum 204 of roller 130 over conduit 
206. 
After the first toner image has been transferred to copy sheet 194 at 
transfer station 114, vacuum roller 124 separates sheet 194 from 
transferable relationship with belt 12 and in association with roller 130 
moves it along path 128. When the leading edge of sheet 194 is 
repositioned in transferable relationship with the second toner image on 
belt 12, the vacuum in plenum 138 is removed and sheet 194 travels with 
belt 12 to transfer station 122 where the second image is transferred onto 
sheet 194. Thereafter, a second copy sheet positioning apparatus 158 (FIG. 
1) removes sheet 194 from transferable relationship with belt 12 and 
repositions it in transferable relationship with the third toner image on 
belt 12. Apparatus 158 is similar in construction to apparatus 120 and 
includes first vacuum roller 156, second vacuum roller 208 and vacuum 
plenums 212 and 214 located between rollers 156 and 208. Roller 208 is 
operated in synchronism with roller 156 by means of stepper motor 210 
linked to rollers 156 and 208 and vacuum plenum 212 and 214 located 
between rollers 156 and 208. Vacuum plenum 212 has been moved to a closed 
position by solenoid 216 so that after sheet 194 has been separated from 
belt 12 by roller 156, it moves along second path 218. 
Copy sheet positioning apparatus 158 then repositions sheet 194 in 
registration with the third toner image on belt 12 which is transferred to 
sheet 194 at transfer station 161. Thereafter, sheet 194 is removed from 
transferable relationship with belt 12 at roller 19 by means of third copy 
sheet positioning apparatus 168 which includes vacuum rollers 166 and 218 
rotated in synchronism by stepper motor 220. Apparatus 168 also includes 
vacuum plenums 222 and 224 located between rollers 166 and 217. Solenoid 
226 has moved plenum 224 to its closed position so that when roller 166 
has removed sheet 194 from transferable relationship with belt 12 sheet 
194 is moved along a second path 228. 
Sheet 194 is repositioned in transferable relationship with belt 12 in 
registration with the fourth toner image thereon. The fourth image is 
transferred to sheets 194 in superimposed relationship with the first, 
second, and third toner images at transfer station 172. Thereafter, sheet 
194 is separated from belt 12 at roller 20 and transported by means of 
vacuum transport 178 to the nip of fuser rollers 180 and 182 which 
permanently fuse the toner images to sheet 194. Sheet 194 is then fed to 
output tray 184. 
The order of color separation image exposure, development, and transfer is 
selected in order of decreasing influence on sharpness of the reproduced 
composite image; for example, black, then cyan, then magenta, then yellow. 
Accordingly, the four transferred images yield a sharp full color 
reproduction of the original on the copy sheet. The employment of four 
separate transfer corona charges and three separate copy sheet positioning 
apparatus interposed between the transfer charges provides for more 
accurate control of image transfer and superimposed image registration. 
Although the present invention has been described above with respect to 
copy sheets of first and second dimensions, it will be understood that 
copy sheets of other dimensions may be utilized in the present invention. 
Moreover, although four toner images have been described as being 
transferred in superimposed relationship upon a copy sheet, more or less 
number of superimposed images may be transferred to a copy sheet. In 
addition, other colors than black, cyan, magenta, and yellow may be used. 
The invention has been described in detail with particular reference to a 
preferred embodiment thereof, but it will be understood that variations 
and modifications can be effected within the spirit and scope of the 
invention.