Variable force document handling system

An improved document handler for transporting and registering document sheets over the platen of a copier, having first and second plural sets of document transport belts extending in the direction of document transport over the platen, with the first set of belts being transversely interdigitated with the second set of belts, with the first set of belts having a substantially higher frictional driving force on document sheets than the second set of belts other than in said registration area to predominantly control the transporting of a document sheet over the platen except in the registration area, and with the second set of belts being more closely positioned to the registration area of the platen than the first set of belts and driven at a slightly higher speed so as to predominantly control the transport of a document sheet in the registration area during its registration.

The present invention relates to a document handling system and more 
particularly relates to an improved method and apparatus for automatically 
transporting, registering and deskewing individual document sheets to be 
copied on a copier platen utilizing different transport belts. 
As xerographic and other copiers increase in speed, and become more 
automatic, it is increasingly important to provide higher speed yet more 
reliable and more automatic handling of the original document sheets being 
copied, i.e. the input to the copier. It is desirable to feed, register 
and copy document sheets of a variety or mixture of sizes, types, weights, 
materials, conditions and susceptibility to damage, yet with minimal 
document jamming, wear or damage by the document transporting and 
registration apparatus, even if the same documents are automatically fed 
and registered repeatedly, as for recirculating document precollation 
copying. 
Even with slower copying rate copiers, it has become increasingly desirable 
to provide at least semi-automatic document handling, allowing an operator 
to "stream feed" originals into an input of the copier document handler, 
with the document handler doing the deskewing, final registration and 
feeding of the documents into and through the copying position, and then 
ejecting the documents automatically. However, for compact and low cost 
copiers, an appropriate document handler must also be simple, low cost and 
compact. 
A preferably document handling system is one that utilizes an existing or 
generally conventional copier optical imaging system, including the 
external transparent copying window (known as the platen) of the copier. 
It is also desirable that the document handling system be readily 
removable, as by pivoting away, to alternatively allow the copier operator 
to conventionally, manually place documents, including books, on the same 
copying platen. Thus, a lighter weight document handler is desirable. It 
is also desirable for the same registration edge or position to be 
available for such manual copying as is used for the document handler. 
In the description herein the term "document" or "sheet" refers to a 
conventional flimsy sheet of paper, plastic, or other conventional or 
typical individual image substrate (original or previous copy), and the 
like, and not to microfilm or electronic image originals which are 
generally much easier to manipulate. However, the terms "copier" or 
"copying" here are intended to encompass electronic document reading 
devices which record or transmit the information read from the document in 
electronic or other form not limited to copy sheets. 
Although faster and more accurate automatic registration of the individual 
original document sheets at the correct position on the platen to be 
copied is desired, it is difficult to accomplish without skewing (slightly 
rotating) the document and/or damaging the edge of the document being 
stopped. Document sheets can vary widely in sheet size, weight, thickness, 
material, condition, humidity, age, etc.. Documents may have curls, 
wrinkles, tears, "dog-ears", cut-outs, overlays, paste-ups, tape, staples, 
adhesive areas, or other irregularities. Unlike copy sheets, which 
generally are all from the same batch and cut from the same paper reams, 
and therefore of almost exactly the same condition and size, original 
document sheets often vary considerably even if they are all of the same 
"standard" size, (.e.g. letter size, legal size, A-4, B-4, etc.) because 
they have come from different paper batches or have variably changed size 
with different age or humidity conditions, etc.. Yet it is desirable to 
automatically or semi-automatically rapidly feed, register and copy a set 
of individual documents with a mixture of sizes, types, and conditions 
without document jams or document damage and with each document correctly 
and accurately aligned to the registration position. 
One of the most difficult to achieve requirements for automatic document 
handling is the accurate and reliable, but safe, registration of the 
original document at the proper position for copying. Conventionally the 
document is desirably automatically either center registered or corner 
registered (depending on the copier) by the document handler at a pre-set 
registration position relative to the copier platen, with two orthogonal 
edges of the document precisely aligned with two registration lines of the 
copier platen i.e. with the original document aligned with the copier 
optics and copy sheet registration system. This registration accuracy is 
desirably consistenly within less than 1 millimeter. If the document is 
not properly registered, then undesirable dark borders and/or edge shadow 
images may appear on the ensuing copy, or information near an edge of the 
document may be lost, i.e. not copied onto the copy sheet. Skewing can 
also affect proper restacking of the documents. 
As shown in the cited art, document handling systems have been provided 
with various document transports to move the original document sheets over 
the copier platen and into and out of registration. Various combinations 
of such transports are known with various registration devices or systems. 
It is known in the art to register the original document for copying at 
the appropriate position relative to the transparent copying window in 
various ways. Typically the document sheet is registered by driving it 
against a gate or stop at or adjacent one edge of the platen. This may 
comprise projecting aligned fingers, or roller nips, or a single vertical 
surface, against which an edge of the sheet is driven into abutment to 
register the sheet. An important function of such registration is to also 
deskew the moving original document, i.e., to properly rotate and align it 
with the registration line as well as to determine and control its 
registration position. 
As indicated, it is conventional to provide either fixed or retractable 
registration finger or gate document stopping edges aligned along the one 
edge of the platen, so as to physically register the document in its 
copying position. This also reduces transport criticality, i.e. allows 
slip or skewing of the document feeder to be accommodated and corrected. 
The document transport can be designed to slip briefly relative to the 
document lead edge striking the registration edge stop until positive 
deskewing and full registration are achieved. However, the same platen 
transport sheet feeder is preferably used to drive a document onto and off 
of the platen before and after copying as well as registering the lead 
edge of the document at the downstream platen edge. Registering the trail 
edge of the document by reversing the feeder and backing the document into 
a fixed registration edge at the upstream edge of the platen may be 
alternatively provided. In some document handling systems a system for 
also side registering or laterally positioning the document on the platen 
is used, i.e. positioning of the original on two axes on the platen. 
However this is not required, and lateral registration may be done 
upstream of the platen. 
A severe limitation on such frictional over-platen document sheet transport 
and registering systems is that they must have sufficient drive force to 
reliably feed the document sheet, but must slip relative to the platen 
glass when no document sheet is therebetween without scratching or wearing 
the glass such that imaging through the glass is affected. As indicated 
above, the document transport normally needs to also slip relative to the 
document when the document is stopped by the registration edge stop. 
Further, the over-platen transport should minimize "show around" problems 
- i.e. undesirable dark areas or images on the copy sheet, especially for 
undersized documents, by visible portions of the transport extending 
beyond the document edges during copying. This has led to the use of 
single large white elastomeric belts for many document handlers in lieu of 
rollers or multiple belts, but such single belt systems have some inherent 
compromises in feeding and registration reliability. This is discussed, 
for example in U.S. Pat. No. 4,353,541 issued Oct. 12, 1982 by W. J. 
Parzgnat and the art therein, which includes solenoid actuated "kicker" or 
normal force belt loading rollers. Such an intermittently actuated platen 
transport belt backing or kicker roller is also disclosed for a narrow 
belt in U.S. Pat. No. 4,146,220 issued Mar. 27, 1979 to Peter Barton, to 
likewise alter the frictional driving force between the belt and the 
document. 
Examples of the peculiar or special requirements for platen transport belt 
material (compared to other belts) are disclosed in U.S. Pat. No. 
4,314,006 issued Feb. 2, 1982 to James A. Lentz and Joseph H. Moriconi. 
A particular such limitation or compromise is that a document transport 
system which minimizes the introduction of document sheet skewing in 
feeding from the document set stack up to the registration position on the 
platen is highly desirable, in order to reduce the amount of skew needing 
correction (deskewing) in the registration position. Yet it is also 
desirable, but normally incompatible, to maximize document skewing during 
the document registration, i.e. to allow the document to be freely 
deskewed as it is driven into alignment with the registration edge. The 
present invention compatibly provides both of these features. 
The present invention may be utilized as part of a recirculating document 
handler as well as for an automatic or semi-automatic document handler. 
Some examples of further details of exemplary recirculating document 
handlers with on-platen registration document transport and deskewing for 
which the present invention may be substituted are disclosed in U.S. Pat. 
Nos. 4,335,954 issuing June 22, 1982 to Russell L. Phelps; 4,278,344 
issued July 14, 1981 to R. B. Sahay; 4,270,746 issued June 2, 1981 to T. 
J. Hamlin and 4,076,408 issued Feb. 28, 1978 to M.G. Reid, et al.. 
Various plural or multiple belt document sheet transport systems for copier 
platens are known, including the following examples: U.S. Pat. Nos. 
3,844,552 issued Oct. 29, 1974 to C.D. Bleau et al; 4,322,160 issued Mar. 
30, 1982 to G.S. Kobus; and the art cited or discussed therein; and IBM 
Technical Disclosure Bulletin Vol. 15, No. 2, July 1972, pp. 389-390. The 
latter shows two sets of belts - feed belts 12 and backup belts 16. These 
references also disclose a registration advantage of plural belt systems 
in that retractable or fixed platen registration edge fingers can extend 
between the plural belts, and vice-versa, for preventing the document from 
slipping past the fingers during registration. 
In technologies or arts other than original document sheet platen transport 
and registration systems there are, of course, many other multiple belt 
systems, per se. Examples include copy sheet feeding, wherein U.S. patent 
application Ser. No. 385,626 filed June 7, 1982 by John Maksymiak 
(D/80278) discloses plural frictional copy sheet feeding belts wherein 
each belt has alternating and oppositely matched sections therealong of 
different coefficients of friction. Other flexible sheet conveyors in 
other applications are known with cooperative belts of different 
coefficients of friction, e.g. U.S. Pat. No. 4,190,185 issued Feb. 26, 
1980 to Kurt Thate and 4,085,929 issued Apr. 25, 1978 to K. Tuchiya et al. 
Examples of various other patents teaching document handlers and also 
control systems therefor, including document path switches, are U.S. Pat. 
Nos.: 4,054,380; 4,062,061; 4,076,408; 4,078,787; 4,099,860; 4,125,325; 
4,132,401; 4,144,550; 4,158,500; 4,176,945; 4,179,215; 4,229,101; 
4,278,344 and 4,284,270. Conventional simple software instructions in a 
copier's conventional microprocessor controller logic circuitry and 
software of document handler and copier control functions and logic, as 
taught by these above and other patents and various commercial copiers, 
are well known and preferred. However, it will be appreciated that the 
document handling functions and controls described herein may be 
alternatively conventionally incorporated into a copier utilizing any 
other suitable or known simple software or hard wired logic systems, 
switch controllers, etc.. Such software for functions described herein may 
vary depending on the particular microprocessor or microcomputer system 
utilized, of course, but will be already available to or readily 
programmable by those skilled in the art without experimentation from the 
descriptions provided herein. 
All references cited herein, and their references, are incorporated by 
reference herein for appropriate teachings of additional or alternative 
details, features, and/or technical background. 
The present invention desirably overcomes or reduces various of the 
above-discussed problems. A desirable feature of the document handling 
system disclosed herein is to provide a document transport for a copier 
platen which automatically provides a lighter driving force during 
registration of the original document sheet on the platen than the driving 
force on the document when the document is entering onto the platen, so as 
to provide reliable feeding yet reduce the chances of buckling or damaging 
the document during that portion of its transport in which it is being 
registered, thereby overcoming a tendency of many present document 
transport belt systems to provide either too much or too little document 
driving force for one or both of these different transport portiions and 
conditions. 
A preferred feature disclosed herein is to provide, in a document handler 
for transporting, with a plural driven belt sheet transport, and 
registering document sheets over the platen of a copier, said registration 
being to an area adjacent one side of said platen, the improvement 
comprising: first and second plural sets of document transport belts 
extending in the direction of document transport with said belts of said 
first set of belts being transversely inter-digitated with said belts of 
said second set of belts over said platen, said belts of said first set of 
belts having a substantially higher frictional driving force on document 
sheets than said belts of said second set of belts, and said belts of said 
second set of belts being differently positioned relative to said 
registration area of said platen from said belts of said first set of 
belts so that said lower frictional driving force belts of said second set 
of belts predominantly control the transport of a document sheet in said 
registration during registration of that document sheet. 
Further features which may be provided by the method and apparatus 
disclosed herein, individually or in combination, include those wherein 
said second set of belts is mounted to normally engage a document sheet on 
the platen at or adjacent said registration area of said platen; said 
first set of belts is mounted normally spaced from said platen in said 
registration area for driving said belts of said second set of belts 
faster than said belts of said first set of belts during at least the 
registration of a document sheet in said registration area of said platen; 
said first set of belts is normally spaced from but extending over said 
registration area of said platen, and wherein sheet ejection means are 
provided for intermittently forcing a portion of the belts of said first 
set of belts towards said platen at or adjacent said registration area for 
assisting in the ejection of a document sheet from the platen after the 
document sheet has been registered; said belts of said second set of belts 
are driven faster than said belts of said first set of belts and have a 
higher coefficient of friction than said second set of belts relative to a 
document sheet; said first set of belts is mounted to normally engage said 
platen at or adjacent a side thereof opposite from said registration area 
of said platen so that first set of belts predominantly controls the 
transport of a document sheet during the initial transport of a document 
sheet onto said platen; and wherein the platen overlying flights of said 
first and second sets of belts are oppositely slightly angled relative to 
said platen and relative to one another. 
Another disclosed feature is a method of transporting document sheets onto 
and over a copier platen and into registration frictionally with plural 
frictional transport belts extending over the platen, and registering the 
document sheet in a copying position on the platen by frictionally driving 
the document sheet against a registration edge stop at or adjacent at 
least one edge of the platen with said frictional transport belts, 
comprising the steps of initially feeding a document sheet onto the platen 
primarily with a first plural set of higher frictional force transport 
belts which resist document sheet skewing and slipping, and then gradually 
transferring normal transport control of said document sheet to a second 
set of lower frictional force transport belts which allow greater document 
sheet skewing and slippage as the document sheet is transported over the 
platen by both said sets of belts towards said registration edge stop. 
A further disclosed feature is wherein said gradual transfer of transport 
control is in proportion to the distance moved by the document sheet over 
the platen and is accomplished with movement of said transport belts in 
different paths which are slightly differently angled from one another 
over the platen. 
Various of the above-mentioned and further features and advantages will be 
apparent from the examples described hereinbelow of specific apparatus and 
steps of operation. The invention will be better understood by reference 
to the following description of one specific embodiment thereof including 
the following drawing figures (approximately to scale) wherein: 
FIG. 1 is a side view of an embodiment of an exemplary document handling 
apparatus utilizing the document transport and registration system of the 
present invention; and 
FIG. 2 is a plan (top) view of the apparatus of FIG. 1.

The exemplary document sheet handling system disclosed in FIG. 1 may be 
conventional except as otherwise described herein, and may be mounted to 
any suitable or conventional copier. Disclosed here as one example, but 
not limited thereto, is a semi-automatic document handler (SADH) unit 10. 
It is conventionally mounted over a conventional copier platen, preferably 
pivotably removable for alternative manual document placement on the 
platen. Alternatively, however this document handler 10 may be the platen 
transport portion of a recirculating document handler providing 
precollation copying. A document sheet 12 may be conventionally fed to the 
upstream end or entrance to the document handler 10, either manually or 
automatically fed from a stack of document sheets, as is known in the art. 
The document handler 10 receives the document sheet 12 and is designed to 
transport it reliably into the platen registration position for registered 
imaging thereof by the copier. Registration here is illustrated by a 
conventional retractable registration edge stop 13 at the downstream edge 
of the copier platen 14. As previously discussed, the requirements for the 
transporting of the document into the platen registration area 15 are 
different from the desired feeding forces on the document both prior and 
subsequent thereto. In the platen registration area 14 the document 
transport must slip relative to the document sheet 12 to prevent buckling 
or overdriving of the lead edge of the document sheet against the fingers 
or gates of the registration edge stop 13. Also it is desirable to allow 
the document sheet to skew slightly during this final movement thereof 
into registration so as to allow the transport to align the document to 
the line of the registration edge. 
This registration skewing and slipping allowance is however, quite 
inconsistent with the desired non-skewing upstream feeding of the document 
before it reaches the registration area 15. It is also inconsistent with 
the desired rapid and non-skewing downstream ejection of the document from 
the platen after copying of the document is completed. That is, after the 
document has been registered and illuminated for exposure, it is desirable 
that the registration edge stop 13 be lowered out of the document path by 
a solenoid or other suitable mechanims and that the same document 
transport then be usable, by itself or with limited assistance, to rapidly 
eject the document from the downstream edge of the platen into a suitable 
catch tray or the like, and also to simultaneously rapidly feed on the 
next document to be copied. This ejection requires rapid acceleration of 
the document sheet which increases potential slippage or skew problems, 
both for the document being ejected and for the next document being fed in 
at high speed at the upstream or input area of the platen and its 
transport. 
Here the platen transport is provided by two sets of document feed belts 
extending over the platen which are differently mounted and preferably 
also have different coefficients of friction, yet which are cooperatively 
inter-digitated and angled relative to one another and the platen to 
provide a desirable variable feeding force system for the documents, 
varying with the position of the documents on the platen and overcoming 
various of the abovedescribed problems. This exemplary transport and 
registration system here includes a first set of belts 16 comprising a 
plurality of high friction belts 18. These are inter-digitated with a 
second set of belts 20 comprising low friction belts 22. These are all 
belts which are narrow relative to the platen width and spaced apart 
sufficiently to allow the inter-digitation of the fingers of the 
registration edge stop 13 at the downstream end thereof for reliable 
document registration. With the illustrated arrangement the high friction 
belts 18 alternate side by side with the low friction belts 20 
transversely across the platen. However both the high friction and low 
friction belts (both sets of belts) extend in the same document movement 
direction and both are adopted to engage and feed the document sheet, but 
not in the same manner, as will be described. 
The belts 18 and 22 may be constructed from commercially available document 
belt materials for frictional platen transport document handlers. Examples 
of document belt materials are disclosed in the abovecited U.S. Pat. No. 
4,314,006 issued Feb. 2, 1982 to James A. Lentz and Joseph H. Moriconi and 
in references cited therein. The differences in the coefficient of 
friction may be provided by changes in the formulation of the document 
belt material. For example, the coefficient of friction may be increased 
by increasing the proportion of polymer by decreasing the amount of 
fillers (non-rubber ingredients), or by using a more elastomeric polymer, 
such as a silicone rubber. Alternatively or additionally, the two 
different coefficient of friction belts may have different surface 
characteristics formed, for example, by molding, calendering, sanding, 
coating or otherwise treating the belt surface during manufacture. The 
higher friction belts 18 are thus shown with stippling on the surfaces 
thereof for illustration purposes in FIG. 2. However, as indicated, a 
difference in surface characteristics is not required, and both surfaces 
should be optically uniformly reflective for the copier optics so as to 
minimize "show-around" or printout of the belts at the edges of documents 
or "show-through" from behind the documents. 
The differences in the coefficient of friction of the belts 18 and 22, 
relative to the document sheet to be transported, or their absolute 
values, need not be critical with the present system. In fact the 
coefficients of friction may be considerably less critical to maintain 
than for a conventional document belt system, due to the great differences 
here in the applied normal force of the respective belts against the 
document sheet in the registration area versus the feed-in area of the 
platen. That is, in the present system, the document frictional driving 
force, which is a function of both the coefficient of friction and the 
normal force, is substantially and oppositely varied by varying the 
respective relative positions between the two sets of belts and the platen 
as both sets of belts extend across the platen. The first set of belts 16 
is positioned to maximize the normal force of its belts 18 at the input 
area of the platen and the second set of belts 20 is positioned to 
maximize the normal force of its belts 22 in the registration area 15 of 
the platen. 
The two sets of belts are oppositely slightly angled relative to the plane 
of the platen. The first set of belts 16 extends generally linearly from 
contact with the platen (at or adjacent its upstream edge) upwardly at a 
slight angle so that the same lower flight of those belts 18 is normally 
spaced several millimeters above the platen at the registration end of the 
platen 14. In contrast, the second set of belts 20 are positioned such 
that the lower flight of the low friction belts 22 are spaced several 
millimeters above the platen in the input area for the document and then 
extend generally linearly at a slight angle to the platen down into 
contact with the platen in the registration area 15, including extending 
directly over the registration edge stop 13, so as to provide a document 
retaining and normal force nip with a document fed therebetween in this 
registration area (but not in the upstream area of the platen where the 
nip and normal force engagement is between the other belts 18 and the 
platen). 
The different spacing and path of the belts is provided in this example by 
differently mounting the belts on different diameter rollers mounted on 
shafts adjacent opposite ends of the platen. These rollers support and 
tension opposite ends of all of the endless loop belts 18 and 22. As 
particularly shown in FIG. 2, a downstream mounting and drive shaft 24 is 
driven by a motor M to commonly drive on a single axis a plurality of 
small drive rollers 28 and large drive rollers 29. The smaller diameter 
drive rollers 28 both support and drive the downstream ends of the high 
friction belts 18. The larger diameter drive rollers 29 support and drive 
the lower friction belts 22. The slightly larger diameters of the rollers 
29 drive the lower friction belts 22 at a slightly higher sheet transport 
velocity, proportional to the difference in roller diameter. As shown 
particularly in FIG. 1, this difference in diameter between the downstream 
rollers 28 and 29 also controls the difference in spacing of the 
respective belts 18 and 22 from the platen 14 in the downstream or 
registration area 15 of the platen and the approach thereto. 
In contrast, a reversed difference in belt spacing from the platen is 
provided at the opposite upstream or document input end of the platen. 
There an upstream mounting shaft 30 supports small idler rollers 32 and 
large idler rollers 34. It may be seen that at this end the high friction 
belts 18 are mounted on the larger idler rollers 34 and the lower friction 
belts 22 are mounted on the smaller idler rollers 32, i.e. opposite from 
the drive rollers 28 and 29. These idler rollers 32 and 34 are freely 
indpendently rotatable on the upstream shaft 30 to accommodate the 
difference in velocity of the belts and the difference in rotational 
velocity of these pulleys. The idler rollers 32 and 34 provided a 
corresponding but opposite spacing of the belts 18 and 22 relative to the 
platen 14 at its upstream end as contrasted to the downstream or 
registration end of the platen. The larger diameters of the idler rollers 
34 cause the high friction belts 18 thereon to normally engage or form a 
relatively high normal force document feeding nip with the platen 14 in 
this area of the platen. 
Both shafts 24 and 30 are preferably conventionally floatingly or loosely 
mounted in the platen cover unit, so as to allow the belts to conform to 
the platen in their said contact areas with a controlled gravity and/or 
spring loading normal force when the platen cover is closed without any 
spacing or alignment criticality. It may also be seen that two high 
friction belts 18 are laterally positioned to engage opposite sides of the 
conventionally sized document 12, i.e. are widely transversely spaced 
relative the document for maximum document skew resistance and control. 
It may be seen from the above that the lower friction belts 22 of the 
second set of belts 20 engage and normally predominantly control the 
transport of a document sheet in the registration area of the platen 
during the registration of the document sheet whereas the higher 
coefficient of friction belts of the first set of belts 16 engage and 
predominantly control the transport of the document sheet upstream 
thereof, and especially in the document input area. However there is a 
smooth, continuous and overlapping transition in the control of the 
document by the two sets of belts as they cooperatively feed the document 
across the platen. The relative spacing and control of document feeding 
changes gradually from one set of belts to the other as the document moves 
from one side of the platen to the other. Also, at least some part of the 
document is under the direct control of at least one of the sets of belts 
at all times, i.e. it is not free of, or released from the document 
transport at any time here. This transition in transport control is not 
only a function of the gradual transition in normal force with the 
transition in the relative spacings of the two sets of belts from the 
platen with changes in position of the document on the platen, but also is 
a function of the higher velocity of the belts 22 relative to the belts 
18. That is, as the belts 22 gain control of the document near 
registration they, in effect, pull it away from the other belts 18. The 
effect of the higher friction but slower and (in this area) lower normal 
force belts 18 then becomes only a decreasing drag force rather than an 
advancing force. Thus the document advancing force, which determines the 
force with which the document lead edge is fed into abutment and alignment 
with the edge stop 13, is controlled by the belts 22 and not by the belts 
18 during the critical final, registration alignment, movement of the 
document sheet over the platen. The slight drag force of the slower belts 
18 during registration desirably reduces the impact or registration force 
of the document against the registration stop 13. Before this control 
transition occurs there will be, of course, some belt slippage of the 
faster belts 22 over the back of the document sheet, but the betls 22 are 
adapted to do so without damaging the document. Furthermore, the 
difference in velocity between the two sets of belts need not be a 
substantial or significant percentage of the normal document velocity. In 
fact, if desired, this difference in velocity need not be provided, i.e., 
as an alternative system, all of the belts may be driven at the same 
velocity and will still provide significant advantages provided by the 
differences in the document driving force provided by the differences in 
belt orientations relative to platen. However, the combination and 
cooperative affect of all these features is very desirable, and it may be 
seen that it is achieved here in a single integral and simple apparatus. 
That is, the combination of the different diameter drive rollers 28 and 29 
and the different diameter idler rollers 32 and 34 provides both the 
positional differences in normal force and the differences in velocity for 
the two different sets of belts. 
Considering now a further disclosed feature, there is additionally provided 
a method and apparatus for briefly intermittently changing the 
above-described document transport control by changing the normal position 
and normal force of the high friction belts 18 relative to the document 
sheet to assist in ejecting the document from the platen after it has been 
registered and copied. This is a system for intermittently pressing normal 
force or kicker rollers 40 into the back of the high friction belts 18 to 
temporarily deform these belts 18 downwardly into engagement with the 
document sheet at the time when ejection of the document from the platen 
is desired. Kicker rollers are known per se as discussed in the 
above-cited patent to William J. Parzygnat and the solenoid actuated 
references described and cited therein. The rollers 40 may be moved 
downwardly by a solenoid 44 repositioning its repositionable axis shaft 42 
downwardly when the solenoid 44 is actuated. Only as long as the solenoid 
44 is actuated a contact and high normal force and driving control is 
established between the high friction belts 18 and the document in the 
platen registration area 15 under the rollers 40 (which otherwise is 
normally not the case, as described above). Thus the high friction belts 
18 may be utilized to rapidly accelerate and eject the document from the 
platen, without allowing slip or skewing of the document. The slightly 
faster low friction belts 22 already engaging the document there will slip 
slightly relative to the document but in a forward or feeding assistance 
force direction. 
It will be appreciated that while four belts are illustrated in this 
example, and are preferred, that a substantially greater number of belts 
may be provided, particularly for larger sizes of documents. It will also 
be appreciated that while belts all of the same width are illustrated 
here, that belts of different widths may be provided. In fact, this is 
another way in which the frictional or driving force difference between 
the two sets of belts may be provided. That is, if the belts 22 are 
substantially narrower than the belts 18, and/or more flexible or thinner 
or the like, it may be possible to make both sets of belts of the same 
material and still provide an appropriate difference in frictional force 
on the document. That is, to provide such difference only by differences 
in width, weight, tension, or the like in the respective sets of belts. 
However, for maximum effect and control, the above-described difference in 
the coefficient in friction between the sets of belts is preferred, and 
may if desired, be supplemented by these other physical or material 
differences. 
It will be noted that an edge-registered copier and document transport has 
been illustrated. For a center-registered document system the belt 
arrangement may differ. For example, one or two low friction belts may be 
positioned adjacent one another centrally of the platen so as to centrally 
engage the document during registration as does the single (second belt 
from the registration side) belt 22 in FIG. 2. Likewise the higher 
frictional force belts may be repositioned to optimize their engagement of 
the document for skew prevention. 
It may be seen that there is disclosed an improved method of transporting 
document sheets onto and over the copier platen and into registration 
frictionally with plural fricitonal transport belts which extend over the 
platen and register the document sheet by frictionally driving the 
document sheet against a registration edge stop at or adjacent at least 
one edge of the platen with said same frictional transport belts, wherein 
the document sheet is initially fed onto the platen with a first set of 
transport belts which resist document sheet skewing and slippage, and then 
normal transport control over the document sheet is gradually transferred, 
as the document is transported across the platen, to a second set of lower 
driving force transport belts, which second set of belts allows greater 
document sheet skewing and slippage as the document sheet approaches the 
registration edge stop. This gradual transfer of control of the document 
is in proportion to the distance moved by the document sheet across the 
platen. It is preferably accomplished utilizing movement of the transport 
belts in slightly different but inter-digitated paths which are slightly 
differently angled from one another over the platen, and also wherein the 
second set of belts are driven slightly faster than the first set of belts 
and preferably have a lower coefficient of friction. 
The embodiment disclosed herein, and others, are intended to provide a more 
positive and reliable yet gentle and automatic control of the driving and 
registration forces on the document sheet during the entire process of 
feeding, registering, deskewing, and ejecting the document. It will also 
be appreciated that the embodiment described herein is merely exemplary 
and that other variations, modifications, refinements, or alternative 
embodiments may be made by those skilled in the art from this teaching. 
They are intended to be encompassed by the following claims.